Mikaeus, the Unhallowed + Cryptic Trilobite + Heartless Summoning

Mikaeus, the Unhallowed

Cryptic Trilobite

Heartless Summoning

How it works

1. Activate Cryptic Trilobite by removing a +1/+1 counter from it, adding CC that can only be spent to activate abilities.
2. Repeat step 1 until Cryptic Trilobite does not have any +1/+1 counters on it.
3. Cryptic Trilobite dies as a state-based action due to having 0 toughness.
4. Cryptic Trilobite's undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
5. Repeat.

This clever loop turns Mikaeus, the Unhallowed into an engine for infinite activation-only mana by leveraging the stat-shrinking drawback of Heartless Summoning. Because Heartless Summoning gives your creatures -1/-1, Cryptic Trilobite enters the battlefield with zero toughness once you strip away its initial counters, causing it to instantly die whenever it lacks a +1/+1 counter. Fortunately, the "other non-Human creatures" clause on Mikaeus, the Unhallowed grants Cryptic Trilobite undying, ensuring it immediately returns to the battlefield with a counter upon death. You can then tap into Cryptic Trilobite's first ability to remove that very counter for two color-neutral mana, fueling your activated abilities until it dies again to repeat the cycle.