Core Items

First we build "Timewarp". With Time Warp we have even more ability haste and even more magical power. After Dynamo we build "Tainted Scepter" for very good Antiheal and more Magical Power. We also scale great with the passive of the item

• Timewarp
• Tainted Scepter

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If I'm playing with a carry that relies on attack speed or builds more towards attack speed, then I build "Marshall" earlier like after "Crystal Tear". You either have to do the carry according to whether he needs or wants the extra attack speed or you look at what kind of build the carry builds, early items etc.
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• Marshall

Midgame Items (Flex)

We can build "Spellbreaker" to have a little more sustain against certain enemy abilities. "Dynamo" which has a super passive that we can activate with our stun and our ultimate. Also very good base stats. We can build "Galaxy Greaves" to have more mobility on the map depending on the situation. We can build situational "Wraith Leggings" to have some movement speed after an ability hit on the enemy hero and we have bonus magical damage. We also can build "Crescelia" for very good Ability colldowns and little more Damage.

• Spellbreaker
• Galaxy Greaves
• Crescelia
• Dynamo
• Wraith Leggings

Situational Items

We can build "Vanguardian" to have more sustain for ourselves and our teammates. We can build "Golems Gift" to have a little more physical armor and also magical power or we can build "Megacosm" to get the maximum dmg out of the late game.

• Megacosm
• Golems Gift
• Vanguardian

Crest

"Silentium" to cancel many abilities like Gideon Ult or Countess Ult on the carry or enemy Phase Ult.

• Silentium

other Crest Situational

Situational as Crest "Reclamation" to cleanse you and your Teammates from CC. We can also build "Santification" to have an additional shield for our mates or We can play "Tranquility" to heal every 30 seconds scalling with our Magical Power

• Tranquility
• Reclamation
• Santification