Basri's Lieutenant + Metallic Mimic + Altar of Dementia

Basri's Lieutenant

Metallic Mimic

Altar of Dementia

How it works

1. Activate Altar of Dementia by sacrificing another creature with a +1/+1 counter on it.
2. When the creature dies, Basri's Lieutenant's second ability triggers, creating a 2/2 Knight creature token that enters the battlefield with a +1/+1 counter due to Metallic Mimic.
3. Resolve the Altar of Dementia ability, causing target player to mill cards equal to the sacrificed creature's power.
4. Repeat.

This clever loop relies on the seamless interplay of creature types and death triggers to grind through an opponent's library. By setting Metallic Mimic to choose "Knight" as it enters, you ensure that every subsequent token entering your board is automatically beefed up with a +1/+1 counter. This sets the stage for Basri's Lieutenant, whose static death-trigger condition is met the moment you sacrifice that creature to Altar of Dementia, instantly spawning a brand-new 2/2 Knight token to replace it. Because that new token enters with its own counter thanks to the Mimic, the cycle can repeat indefinitely to mill out the table.