Infinite Reflection attached to Cultivator Colossus.
Steps
Play any land from your hand.
The land enters the battlefield as a copy of Cultivator Colossus due to Nature's Revolt and Infinite Reflection.
When the land enters the battlefield, it triggers.
Holding priority, activate Altar of Dementia by sacrificing the land.
When the land dies, Mortuary triggers, putting the land on top of your library from your graveyard.
Resolve the Altar of Dementia ability, causing target opponent to mill cards equal to the land's power.
Resolve the land's trigger from step 3, causing you to put any other land onto the battlefield from your hand, draw a card, and then decline to put another land onto the battlefield.