Davion, the Dragon Knight is a semi-carry, best suited for the mid lane, who excels at pushing and team fighting against teams that rely on physical damage. Avoid picking him against teams with lots of magic damage, pure damage, and BKB-piercing spells.
Although he has decent late game potential, your ideal gameplan is to aggressively take objectives and force team fights before the enemy hard carry can come online. Accomplishing this requires a strong laning phase, including stacking ancients that you can farm yourself once you hit level 12 and have Armlet of Mordiggian.
Farming ancients will let you quickly obtain level 15 and Black King Bar. If you can accomplish all of this before 23:00, you will almost certainly be the most powerful hero on the map. Ask your team to join you in walking down lanes and taking objectives. Back off when your ult is down and push again when it is up. Take all T2's like this, then secure Aegis, then push high ground.
This guide is based on my 600+ Davion games (60% win rate) plus countless hours watching pros and talking to 6k+ mid players about Davion. I am confident that this guide will help you understand Davion on a new level and, most importantly, help you to win games.
Durability. Due to his passive, Dragon Blood, his above-average agility growth for a strength hero (4th highest), and the damage reduction caused by Breathe Fire. This makes him hard to push out of lane and let's him tank physical damage in team fights and pushes for long periods of time.
AOE Damage. Breathe Fire is a strong AOE nuke and Elder Dragon Form level 2+ adds splash damage to his auto-attack, making him very strong against illusion heroes. The latter also lets him clear large jungle camps very quickly.
Pushing. Davion is a great pusher, for three reasons. 1) Elder Dragon Form level 1+ adds 100 magic damage over 5s to his auto-attack. 2) His AOE damage lets him clear creep waves quickly. 3) His durability allows him to tank creep waves and towers so that his allies can push longer.
Disabler. Although never picked primarily for this reason, Davion has one of the best stuns in the game, Dragon Tail, which has a low mana cost, short cooldown, very long duration, and fast projectile speed. The downside is its range is melee while in knight form.
Low attack damage. Although Elder Dragon Form adds 20 magic DPS for 5s to his attack and his splash damage amplifies it in a way, he needs to obtain a damage item like Armlet of Mordiggian and his level 15 damage talent before he can really pack a punch.
Magic and pure damage. Davion is usually in the middle of team fights and pushes, yet his armor does nothing versus magic and pure damage. Against magic damage, we get items like Infused Raindrops until we can finish a Black King Bar or occasionally a Hood of Defiance. Against both magic and pure damage, we will prioritize strength-gain items that increase our HP.
See Dotabuff's matchups for Davion for a full list of friends and foes.
DAVION'S FAVORITE TEAMMATES
I like teammates that shore up Davion's weaknesses, keep the enemy grouped, or can keep me live when tanking.
Drow Ranger. Her aura boosts your damage while in dragon form, her ice arrows keep the enemy close, and her silence adds some utility that you don't have. She works great with a frontliner like Davion.
Luna. Her aura boosts your damage when she's near, she offers your team a good mix of magic and physical damage, and she gives your team hard carry potential. She also works great with a frontliner like Davion.
Io. Tether makes you even tankier and greatly increases your mobility. Relocate ganks are powerful so long as you can stun the enemy, which may require Blink Dagger so you don't need to commit dragon form.
Magnus. If you can't imagine why Magnus is a great teammate, watch this immediately.
Enigma. Another pusher whose ult also rivals Magnus' in terms of keeping enemy grouped.
Underlord. Having Underlord on your team means he's not on the other team, which is a good thing since he counters you hard with his damage-reuding Atrophy Aura and percentage-based damage from Firestorm. Obviously his ult is great for enabling risky pushes or faster deathball.
Usually you will max Breathe Fire first, because it aids fighting, harassing, pushing, and farming. The debuff it causes to enemy attack damage is very significant in lane, as you can use this early on to mess up the enemy's last hits and neutralize ganks. In lane, you'll also use it to harass and secure last hits. In team fights, prioritize hitting carries early on the in the team fight, unless you're try to kill off a support immediately.
Dragon Tail is one of the longest stuns in the game and the longest guaranteed stun at level 1. Since it costs a lot of mana and does little damage, its only purpose in lane is to secure a kill or shut down a gank. The stun duration and damage also scale poorly, so an early value point (usually level 4, 5, or 7) is appropriate and then you don't need to skill it again until you have nothing else to skill.
Dragon Blood lets you easily tank physical damage and wield Armlet of Mordiggian and Soul Ring. It is usually maxed second, with 1-4 points skilled in lane depending on how much harass you're taking. The HP regen is constant and therefore will restore you to full health more quickly if your total HP is low, which is why if you're not fighting or farming you should turn your Power Treads off of STR and put high STR items in your backpack while you regen.
ELDER DRAGON FORM
Typically you should skill Elder Dragon Form when you can. Use your dragon form when a team fight breaks out, you want to push quickly, or you need to farm ancient stacks. On occasion you will use it to escape, since it provides +25 MS. In the late game, reserve it for team fights only, because you will be severely handicapped if you're forced to fight in knight form.
Some comments on the attack modifiers provided by Elder Dragon Form:
Corrosive Breath. Applies a debuff to the target that deals 20 magic damage per second for 5 seconds. Successive attacks refresh the duration. Since it is magical, it is not reduced by armor, which is why Davion destroys buildings so quickly. You can also buy yourself a few seconds by walking away from the tower when it is low and letting the poison destroy it. Before you have Splash Attack, you can push faster by switching targets on every attack so that the debuff is applied to more enemies.
Splash Attack. Corrosive Breath is applied to all enemy units within the 300 splash radius. Splash does not affect structures but enemy units can be splash damaged if Davion is attacking a structure. The splash damage decreases the further the unit is from the primary target.
Frost Breath. Reduces the movement and attack speed of all enemy units in splash radius by 30% and 30, respectively. Pierces spell immunity, which allows Davion to kite heroes like Sven.
The talent selections listed at the top are situational, but ideal. View the win rates of each talent here.
Level 10. Both talents are very good but the mana regen talent is arguably better since it basically guarantees you never have to return to fountain. The Breathe Fire talent is a also a waste if you're not adept to using it on the enemy carries at the start of a team fight.
Level 15. Only get the HP talent if you're main purpose is to tank and your other cores provide sufficient right-click damage. Getting the damage talent is one of Davion's biggest power spikes and a great opportunity to push or fight.
Level 20. The Dragon Blood talent is usually vastly superior to the GPM talent, with a few notable exceptions: 1) the game is certain to go very late, 2) you're not tanking, 3) your passive will get broken every team fight (e.g., Silver Edge, Nethertoxin), 4) your main concern is magic damage (in which case you will need to buy anti-magic items).
Level 25. The strength talent is going to boost your damage, HP, and magic resistance by a significant amount all at once. I would only recommend the stun duration talent if your team is in desperate need to locking down a nimble core like Weaver, Puck, or Anti-Mage.
By 15 minutes, you want to have Armlet of Mordiggian. I agree with Purge that Armlet is "the most Dragon Knight item ever". At level 12 you should be doing over 200 damage with Armlet active, not to mention the additional armor. This gives you a huge edge over other cores in the early game. Dragon Blood largely mitigates the HP drain and once you get the 2x Dragon Blood talent, your HP regen will actually exceed the HP drain and you can leave Armlet activated by default.
The usefulness of Armlet increases even more once you become effective at "Armlet toggling". I strongly recommend that you practice this in a lobby until you feel comfortable with it. Skillful Armlet toggling can make a hero like Davion incredibly difficult to kill and result in some stellar outplays. Nevertheless, if you're certain you're not comfortable with the item, I'd recommend Drum of Endurance or Shadow Blade instead.
In the deathball strategy that I prefer, the most important item you can have is Black King Bar. It's not essential in every game, but to keep things simple I recommend it as a core item. I also generally recommend building it before a mobility item for the simple reason that you don't need a mobility item to siege towers. This will force the enemy to initiate on you. When they do, pop BKB and crush them.
In only a third of my Davion games do I complete a 5000+ gold item, simply because the game is usually over before the such items are necessary. In most games, you don't want to give the enemy any breathing room. You simply want to take high ground and end, which means building cost-effective, high-impact items like Sange and Yasha, Heaven's Halberd, Hurricane Pike, or Drum of Endurance.
When the game does go long or you are simply filthy rich, here are your options:
Assault Cuirass. Buy this if your team needs armor, additional pushing power, or break is regularly removing your passive. If you alone need to tank more physical damage then Heaven's Halberd is a much bigger bang for your buck because the 25% evasion is vastly superior to the mere 7% extra physical resistance that AC will give you if you got the 2x passive talent.
Heart of Tarrasque. Buy this against teams with huge magic damage and disables that need to burst you down in order to win the team fight. The extra HP and magic resistance will keep you alive a long time in fights.
Satanic. When you need more durability but also more damage. Much of the value is lost if you can't attack an enemy during the active, therefore consider targeting lane creeps or going into the jungle. If you want to use it on an enemy hero, use it during BKB, after you've stunned that enemy, or with the active of Hurricane Pike (which will guarantee four fast hits while you're in dragon form so long as you don't lose vision of them).
Eye of Skadi. This is a great all-purpose late game item when you need to tank a mixture of physical and magic damage and also want to kite spell immune / BKB wielding carries even harder.
Mjollnir. Strong against illusion heroes and Assault Cuirass. Let's you farm faster and push harder. Practical pickup versus mega creeps. Don't forget to turn on the shield as a fight breaks out.
Bloodthorn. Everything that can be said about Bloodthorn can be said about Orchid: more damage, more mana, an answer to Linken's, and a silence. One of the only items Davion can get that provides solo pickoff potential. Downside: offers no durability.
Nullifier. Great against heroes like Shadow Fiend that are very reliant on BKB, Eul's, Shadow Blade, Force Staff, etc. Offers a way to pop Linken's.
Linken's Sphere. An underrated pickup on Davion. This solves your mana problems and indirectly makes you tankier by shutting down point target disables that might cripple you late game.
If the game goes late, I would recommend you dedicate slots accordingly: Boots, Mobility Item (i.e., Blink Dagger, Shadow Blade, Force Staff), Armlet, BKB, Durability Item (AC, Heart, Satanic, Skadi), Damage Item (Daedalus, MKB).
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If you're new to Davion I'd recommend you not even read this section and instead focus on developing your skill with the standard build I provided. Otherwise, here are some situational items that I build in <10% of my games:
Radiance. This is a very good item for punishing 3+ core enemy drafts, if your lane goes smoothly. This completely changes your itemization since you will want to get it after you have your lane items (Wand, Treads, etc).
Mask of Madness. If you're snowballing and can afford to delay or skip BKB, getting this along with Armlet and your AS and damage talent will let you do nearly 500 DPS at level 15.
Hood of Defiance. Worth getting before or after Armlet if you find yourself against an absurd amount of nuke damage, since BKB won't come quickly enough. Also a reasonable BKB replacement if you're behind.
Daedalus. I never build this. Every other big item offers some kind of utility that I find more valuable than just raw damage.
ROSHAN DROPS: AEGIS, CHEESE, AND REFRESHER SHARD
Let's get Refresher Shard out of way: Davion probably won't benefit from it as much as one his teammates so I can't recall ever taking this. As for Aegis and Cheese, they're both good but which one you take could affect how you use your ult in your next fight.
If you have Aegis, you should initiate / tank while in melee form, soak up as many spells as possible, and then use your ultimate and BKB when you respawn. The reason is simple: if you die while in dragon form, you will not respawn in dragon form and your ultimate will be on cooldown, which is very bad.
This is why I often prefer Cheese over Aegis: you have the luxury of starting the fight in dragon form and you will remain in dragon form after you consume Cheese. Obviously this comes with the risk of getting bursted down so quickly that you don't have the chance to use it, which is why its not always superior to Aegis.
When you playing Davion mid, you balance five objectives: last hitting, rune control, pushing, harassing, and stacking ancients. Generally you want to prioritize farming and getting XP, but stacking ancients is a close second because a key part of your success will be farming said stacks at level 12 for a burst of a gold and XP.
GENERAL MID ADVICE
Don't gank other lanes unless an obvious opportunity presents itself. A power-up rune on Davion isn't a guaranteed kill like on some mid heroes, so staying mid is usually the most reliable option.
Draw creep aggro constantly, for four reasons: First, it brings the enemy creeps in a safer position for last hitting. Second, the creeps you draw will likely aggro your ranged creep, which will give you an opportunity to deny it more easily. Third, it will cause the enemy creeps to die faster than your creeps, meaning you will gain experience faster than the enemy mid. Fourth, since the enemy creeps will die faster, the lane will push, which will give you space to get runes and stack ancients.
I usually skill Breathe Fire first to make last hitting harder for the enemy. Ideally you want to get a last hit when you use it as well. You can use it 3x before a Soul Ring is necessary to replenish mana. For the first few waves, consider pushing the wave into their tower and using Breathe Fire on them when they try to last hit under the tower.
Level 2, 3 and 4 Breathe Fire will put a ranged creep under 50% health. If you don't prep the creep with 2-3 last hits before using said spell, the enemy will likely deny it.
Always skill Dragon Tail early if the enemy has a Pudge or Spirit Breaker, because if you are caught out of position then you're certainly dead unless you can TP out.
Your supports will rarely ward for you, so I recommend buying your own observer ward and placing it close enough to the top rune to give vision of that rune and any incoming roamers. Against Riki, Bounter Hunter, Nyx Assassin, and Mirana, a sentry ward is also worth the investment.
At level 6 you should start pushing the mid tower with Elder Dragon Form, if possible. Otherwise, use your dragon form if it will help you last hit more safely.
It's not uncommon to take the mid tower at anywhere between 8-10 minutes on your own. If you take it really fast and you're way ahead of the enemy then pressuring the T2 is possible. Otherwise, you can keep farming mid into your Armlet or rotate and try to take another T1. If your safe lane carry is free farming, do not push that lane because you'll mess up his or her farm.
ANCIENTS STACKING ADVICE
PLAYING DAVION IN OTHER LANES
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While it's true that Davion is versatile enough to be played as a core in other lanes, I personally have little desire to this. The safe lane isn't so bad but Davion must be played like Chaos Knight in that he is active pushing on the map very early rather than trying to passively farm his way to victory.
Under no normal circumstance should you jungle, but nevertheless it is possible. Get the normal starting items and buy a Soul Ring ASAP. Skill Dragon Blood at levels 1 and 3, otherwise maxing Breathe Fire.