- -4s stun with 410 AoE
- Good pusher
- Awesome damage/cleave buff
- High damage
- Good stat gain
- Spammable Nuke with good damage for harrassing, pushing and lasthitting
- Good base armour
- Huge target
- No escape spell (Skewer 30s cd)
- BKB removes Empower
- Slow AS
Power Treads give you cheap stats and attack speed, switch str to int if you need mana for your skills.
Armlet perfectly fit your role: Dealing as much damage as possible in the seconds where your enemies are stunned. It is quite cheap by the way. Empower just buffs bonus damage from stats, what means that you should cast it after turning Armlet on. If you want you can turn it off after that if you just want to farm instead of killing heroes. Always turn it on if you want to kill somebody.
Mask of Madness is an alternative item to Armlet. You have to decide what you want more: Lifesteal or bonus damage.
Battlefury is your extremely manly cookie cutter item. It gives you a bit mana regeneration that is really needed, damage and more cleave.
Assault Cuirass gives a lot of damage and makes you tankier.
1 fact ... splash crit is just amazing.
HoT boosts your main stat by a ton. It gives you health and dmg.
In late game Treats should be replaced by Boots of Travel. More ganking + pushing.
Buy Arcane Boots if you need mana. It also helps heroes like Earthshaker or Tidehunter, in fact mana dependent heroes with a low mana pool.
Shivas Guard gives your team some useful slow, makes yourself tankier, and you can deal a bit damage. And you have no mana problems anymore
Scythe of Vyse is an amazing item on nearly any hero (the most just need other items more). Hex is mainly to shut down a carry but it is also very useful for ganking in mid/lategame since all of Magnus disables and slows have a high cooldown. No more mana problems and more survivability are cool, too.
Refresher Orb is a very imbalanced item on Magnus. 8 second stun are more than enough time to kill a whole team in late game.
Eul's is a very useful item that solves your mana problems. Combined with Dagger you are very hard to kill.
Pipe can be bought when you play against AoE strats, an early hood makes you quite tanky.
Mekansm is one of the most important items in the game and a must have for every support (get Mek or Pipe)
Vladimirs Offering gives you the needed mana regeneration, allows you to push faster and buffs your melee carries even more.
Blade Mail is a must have if you get focused 24/7.
Buy Drum of Endurance if you need it and nobody has actually bought it but you may skip it if there are other things which are more needed.