Altar of Dementia + Hardened Academic + Obstinate Gargoyle

Altar of Dementia

Hardened Academic

Obstinate Gargoyle

How it works

1. Activate Altar of Dementia by sacrificing Obstinate Gargoyle.
2. When Obstinate Gargoyle dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Hardened Academic triggers, putting a +1/+1 counter on Obstinate Gargoyle.
4. Resolve the Altar of Dementia ability.
5. Repeat.

This loop turns the recursive nature of Obstinate Gargoyle into a mill engine by utilizing Altar of Dementia to sacrifice the Gargoyle over and over. Each time the Gargoyle dies and returns with a persist-generated -1-/-1 counter, Hardened Academic's clever triggered ability senses cards leaving the graveyard and counters that penalty by placing a +1/+1 counter on it. Because these two opposing counters annihilate each other as a state-based action, the Gargoyle is left completely clean of -1/-1 counters and ready to be sacrificed anew, all while Hardened Academic's presence also ensures the Gargoyle stays modified to retain its flying.