The Book of Vile Darkness + Eye of Vecna + Hand of Vecna + True Polymorph + Bloodthirster

The Book of Vile Darkness

Eye of Vecna

Hand of Vecna

True Polymorph

Bloodthirster

How it works

1. On the end step prior to your turn, cast True Polymorph by paying 4, causing Bloodthirster to become a copy of Eye of Vecna.
2. Activate The Book of Vile Darkness by tapping it and exiling it, Bloodthirster and Hand of Vecna, causing you to create a legendary 8/8 Vecna token that has all triggered abilities of the exiled cards.
3. During your next turn, deal combat damage to an opponent using Vecna.
4. Vecna triggers, causing you to untap it and to get an additional combat phase after this one.
5. Repeat from step 3.