Activate Altar of Dementia by sacrificing Metamorphosis Fanatic.
When Metamorphosis Fanatic dies, Blood Artist triggers, causing you to gain 1 life and target opponent to lose 1 life.
Resolve the Altar of Dementia ability.
Activate Altar of Dementia by sacrificing Junji.
When Junji dies, it and Blood Artist trigger.
Resolve the Blood Artist trigger, causing you to gain 1 life and target opponent to lose 1 life.
Resolve the Junji trigger, returning Metamorphosis Fanatic from your graveyard to the battlefield and causing you to lose 2 life.
When Metamorphosis Fanatic enters, it triggers, returning Junji from your graveyard to the battlefield.
Resolve the Altar of Dementia ability.
Repeat.
This clever loop relies on a continuous cycle of sacrifice and resurrection between Junji, the Midnight Sky and Metamorphosis Fanatic, all fueled by Altar of Dementia. When you sacrifice Metamorphosis Fanatic to Altar of Dementia and then sacrifice Junji, Junji’s death trigger brings back the Fanatic, which immediately triggers upon entering to pull Junji right back out of your graveyard. Meanwhile, Blood Artist sits on the battlefield passively converting this endless procession of sacrifices into a fatal drain of life, while Altar of Dementia simultaneously mills your opponents out completely.