Want to be the Lynchpin of your team? The reason why your carries carry on, your map stays brightly lit, and your enemies hide their daughters? Then step into the shoes of the Weaver of Fate.
Oracle is my main hero and has been since 2016. I've put a lot of hours into trying different builds and strategies with him and there's two particular builds that prove highly effective 95% of the time: the Mobile Artillery build and the Priest build.
For those of you who aren't familiar with Oracle, here's a quick rundown. Besides his obvious strengths of Nuking and Healing, his third (and probably his greatest) strength is how often he is underestimated by his enemies. No one expects Oracle to be as OP as he is, especially so early in the game. Players generally know his Ult is a problem but they often forget how quickly Oracle can melt them if he engages in earnest (as early as level 3) even if they have as much as 60% HP.
He hits hard very early on, he keeps allies in-lane during laning phase, he Thanos Snaps low-hp heroes trying to flee, and he keeps the hard carries alive in team fights through the end. Beyond that, he effectively counters most auto attack heroes with his disarm -- this means heroes like Drow, LC, MK, Viper, and Spec will have a hard time if they don't kill Oracle fast.
To maximize team synergy, make sure your team knows how Oracle works so they don't make you chase them down when they need healing.
Teamfight: Critical Factors for Oracle Success
This goes without saying, but it's not as simple as it sounds. As Oracle, you have to pay attention to twice as many things as any other hero. Think of Oracle as the "eye in the sky"; at any given moment you might have to play an offensive role, a defensive role, a sacrificial role, or a babysitter role and the needs may shift multiple times in one fight. To perform as Oracle should, be keenly aware of the following:
1) Status of Allies
This is your #1 priority. Always know who needs healing, make sure to Q any ally with a negative debuff, and anticipate incoming magic attacks so you can W your allies and keep them unharmed. If an ally is getting chased down, root the pursuer. If an ally is caught in a duel with LC, either 'W' LC or Ult your ally.
2) Status of Enemies
Be aware of any and all buffs on your enemies so you can dispell them with Q. Be able to appropriately prioritize using your Nukes for healing or damage.
3) Battle Composition, Hero Position
Be able to anticipate enemy convergence on an ally hero who is out of position or too deep. A well timed anticipatory 'Q' can root multiple enemies and stop a quick kill in its tracks. This is just about as important as being on top of your general healing game. If an enemy auto-attack hero is the lynchpin on the other team, prioritize disarming him with 'W' over saving it for heals early in the fight. If an enemy escape hero is low on health, like Anti-Mage, make sure you Queue your 'Q' and pop off an 'E' before he blinks away. Your Fortune's End will follow him wherever he goes, even all the way back to fountain if he TP's to base. Also, know which enemies are channeling spells so you can Eul's them.
4) Valuable Sacrifice Opportunity
If your team is routed, know when to sacrifice yourself for the greater good. Oftentimes if you throw yourself at pursuers to save your hard carry, you'll be able to get a kill out of it if you Ult yourself and focus down one of their glass cannons. This can also be useful in a team fight depending on circumstances. Often if you get the entire team to focus you down at the start of a fight, your own team can flank or engage in a more advantageous way. One wombo combo that works well is this strategy + Enigma's Ult.
Achieving Perfect Balance
Utilizing Oracle to his full potential isn't as simple as balancing offense with defense; it's about balancing what kinds of offense with what kinds of defense. Each skill is like a double edged sword which creates 4 general vectors of utility rather than just two.
With each action you take in teamfights, you'll need to decide in a fraction of a second if your offense will be damage-based or disable-based, or if your defense will be pre-emptive disables or normal debuff purge/healing.
For instance, what do you do if an ally is being chased in a 1v1, is about to die, has lethal DoT applied on him, your Ult is on CD, and you have only 3 seconds to act? Do you purge your ally with Q and disarm your opponent or disarm your ally (negating the DoT damage) and root your opponent? One doesn't yield the same results as the other, even though on paper the outcomes are virtually identical.
IF the enemy is melee and won't be in melee range for a few seconds, you might want to go for a W on your ally and a Q on the enemy so you can follow up with a damage-free heal on your ally.
IF the enemy is melee and is faster than your ally, you might want to go for a W on the enemy and a purge on your ally -- especially IF the purge AOE will effect the enemy.
IF the enemy isn't a right-click hero and uses magic, you might want to use W on your ally and root the enemy.
Every Oracle skill comes with a big IF. Oracle says it best: "IF is all."
Pros / Cons
Strong Single- and Dual-Target Disabler
Soft Counters Auto-Attack Heroes
Hard Counters Legion Commander and Necrophos
Not Very Item-Dependent
If played well, can make the single biggest difference in the game.
Not Durable Without Ultimate
Susceptible to Ganks
Often Becomes Primary Target in Teamfights by Mid-Game
Damage Dealing Capabilities Fall Off Late Game
If played poorly, can easily cause a big fat L for the team.
When To Pick
Oracle is always a pretty great pick EXCEPT in the following conditions/circumstances:
1) Enemy Team has Axe
2) Enemy Team has Anti Mage
3) Enemy Team has 3+ durable heroes
Exceptionally great times to pick Oracle:
1) Your Team has Legion Commander
2) Enemy Team has Legion Commander
3) Enemy Team is Right Click Hero heavy (2+)
4) Enemy Team has Pudge ('W' counters Pudge disease aura AND Ulti)
5) Enemy Team has Dark Seer
6) Enemy Team is Magic Damage Heavy
7) Your Team has a super durable hero like BB or Centaur
8) Enemy Team has Necrophos
9) Enemy Team has Sniper ('W' counters Sniper's Ulti)
Oracle Pro Tips
1) When casting on enemy heroes, try to always queue up your Q before
2) When close to the enemy target, however, use E *before* Q.
3) When healing friendly heroes cast W before casting E - unless your target is a right click hero engaged in combat; then consider using W on *his* target.
4) Use Q to dispel enemy buffs such as Dark Seer's Ion Shell, rune bonuses like DD, and Omniknight's Ultimate.
5) Use Q to dispel friendly debuffs like slows, roots, and DoT.
6) When VSing heroes that can blink (or are in mid-TP), try to always hold Q for maximum root. Your Q will follow its target through teleportation and a 2.5 second root will negate any extra distance your target gained through blink. It also provides vision.
7) When your Ult is maxed, use it liberally. CD is short enough to allow for non-essential use, such as rapidly healing a low-hp friendly outside of a teamfight.
8) Use your ult to get allies out of nasty situations like Bane's Fiend's Grip or Shadow Shaman's Shackles + Ult combo. Use Ult for its Strong Dispels and not just the extra healing/damage delay.
9) Pairing Eul's + Q = 5 second "root". Start with Eul's, though, since it also grants invulnerability -- then immediately charge Q and wait for the cavalry to clean up.
10) Your maxed out E insta-kills enemy ranged creeps. Capitalize on this.
1) When you've maxed out E, cast it on friendly ranged creeps followed up with 1 attack: Deny your enemy the most valuable creep, *especially* when they're out of EXP range
2) Combine Q, E, and Eul's to pull off a devastating magic-damage combo: E -> Eul's -> E -> Q -> E. The last E should be fired off only if you're sure it'll secure the kill.
2.5) When Q is maxed, reverse the order: go with E -> Q -> E -> Eul's -> E -> Q -> E. CD for your Q should be over by the time you need to cast it the second time. This combo dishes out 2k magic damage before reductions, if Q and E are maxed.
3) Oracle can be the ultimate counter to escape heroes if you go with the Move Speed Talent. Pair that with a blink dagger and no enemy is going to be able to escape from a team fight or gank -- even Bloodseeker, provided your team can catch up to both of you.
4) After popping Rosh's Linkens, use W on him to prevent his attacks.
5) W stops allied creeps in their tracks (no idea why, might be a bug tbh). So, if your creep wave only has one creep in it and you want to slow down your push, cast W on it.
6) After casting Ult, use E -> W -> E -> E* to maximize healing instead of starting with W. *second E only if you can pull it off while W is still active.
COUNTERS and SYNERGY
Which heroes are a significant counter to Oracle?
Axe, Anti-Mage, Shadow Demon, Spectre, Lifestealer, Templar Assassin, Chaos Knight, Phantom Lancer, Bristleback, Terrorblade
Which heroes does Oracle significantly counter?
Legion Commander, Ember Spirit, Dark Willow, Omniknight, Rubik, Ancient Apparition, Silencer, Phoenix, Sniper, Dark Seer, Riki, Pudge, Zeus, Disruptor, Skywrath Mage, Jakiro, Faceless Void, Wind Ranger, Tinker, Shadowfiend,
Which heroes synergize well with Oracle?
Legion Commander, Alchemist, Monkey King, Ursa, Huskar, Bristleback, Shadow Demon, Techies
When your team has any three of these heroes, avoid picking Oracle in lower MMR games (because apparently, too many people don't realize your W NEGATES magic damage)
5) Crystal Maiden
Spend some time thinking about how Oracle synergizes with various heroes. You can create some interesting surprises with the right combos. Below are a a handful of the more imaginative combinations.
1) Oracle's W allows Techies "Blast off!" to deal no self-harm. If Oracle roots enemy with Q and casts W on Techies right before Blast Off!, it's easy kills with no risk to Techies.
2) Carefully spamming E on Terrorblade when he has Ult available in a teamfight allows him to swap HP much quicker -- plus he'll have a ton of residual passive healing after the swap. Don't risk more than one or 2 E's if he's the main target in the fight though. This significantly increases his odds of pulling off an Ult, too, as the enemy won't be able to predict the Ult since damage sources beyond their control are contributing.
3) If the enemy team has AA and one of your teammates got ulted and is about to dip below the health threshold for Shatter, cast E on him to deny AA the kill. Enemy AA Ult + Oracle's E = Deny.
4) Similar to #3, if ally Pudge is in trouble and he's trying to deny himself, give him a hand and spam E on him when he's low. 9/10 times this results in deny.
5) In the same vein, you can deny allies if you Ult them while they are under the effect of Winter Wyvern's ult. If your ally takes enough damage to die at the end of your ult, then the kill will likely be credited to an ally which makes it a Deny.