Soldevi Adnate + Nim Deathmantle + Breaching Hippocamp

Soldevi Adnate

Nim Deathmantle

Breaching Hippocamp

How it works

1. Activate Soldevi Adnate by tapping it and sacrificing Breaching Hippocamp, adding an amount of equal to Breaching Hippocamp's mana value.
2. When Breaching Hippocamp dies, Nim Deathmantle triggers, causing you to pay 4 to return Breaching Hippocamp from your graveyard to the battlefield, and attach Nim Deathmantle to it.
3. When Breaching Hippocamp enters the battlefield, it triggers, untapping Soldevi Adnate.
4. Repeat.

This clever loop relies on Breaching Hippocamp's ability to untap another creature when it enters the battlefield, which conveniently targets the Soldevi Adnate you just used to sacrifice it. Soldevi Adnate converts the Hippocamp into black mana to help fund Nim Deathmantle's resurrection trigger, which brings the Hippocamp right back to the battlefield. Because Nim Deathmantle also reattaches itself to the resurrected creature for that same four-mana investment, the cycle is entirely self-sustaining.