Activate the creature with Metamorphic Alteration attached using Mirror-Mad Phantasm's ability by paying {1}{U}, causing you to shuffle the creature into your library and mill all cards from your library.

Infinite self-mill

Metamorphic Alteration

Mirror-Mad Phantasm

Cast Metamorphic Alteration by paying {1}{U}, attaching it to Medomai, naming Mistmeadow Vanisher and causing Medomai to become a copy of Mistmeadow Vanisher.
Declare Medomai as an attacker.
Medomai triggers, exiling Metamorphic Alteration until your end step.
When Metamorphic Alteration leaves the battlefield, Medomai is no longer a copy of Mistmeadow Vanisher.
Deal combat damage using Medomai.
Medomai triggers, causing you to take an extra turn after this one.
At the beginning of your end step, Medomai triggers, returning Metamorphic Alteration to the battlefield from exile attached it to Medomai, naming Mistmeadow Vanisher and causing Medomai to become a copy of Mistmeadow Vanisher.
Repeat from step 2 each turn.

Combos with "Metamorphic Alteration"