Lullmage Mentor + Anointed Procession + Primal Vigor + Elspeth, Storm Slayer

Lullmage Mentor

Anointed Procession

Primal Vigor

Elspeth, Storm Slayer

How it works

1. Whenever an opponent casts a spell, activate Lullmage Mentor by tapping seven untapped Merfolk, countering that spell.
2. Lullmage Mentor triggers, creating a total of eight 1/1 Merfolk creature tokens.
3. Repeat.

This engine turns Lullmage Mentor into an absolute fortress against your opponents' spells. Whenever a spell threatens you, you tap seven Merfolk to have Lullmage Mentor counter it, which in turn triggers its ability to manufacture a Merfolk token. That base token production is then exponentially amplified by Anointed Procession, Primal Vigor, and Elspeth, Storm Slayer, flooding your board with eight fresh Merfolk every single time you counter a spell. Because you end up with more than enough bodies to immediately pay the tap cost again, you can repeat this loop to permanently lock the stack and swarm the battlefield with an endless tide of creatures.