Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight + Geralf's Messenger + Yahenni, Undying Partisan

Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight

Geralf's Messenger

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing Geralf's Messenger
2. When Geralf's Messenger dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
3. When Geralf's Messenger enters, it triggers, causing an opponent to lose 2 life.
4. Activate Yahenni by sacrificing Geralf's Messenger
5. When Geralf's Messenger dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
6. When Geralf's Messenger enters, it triggers, causing an opponent to lose 2 life.
7. Resolve both Yahenni abilities from step 1 and 4.
8. Repeat.