Cast Traveling Plague by paying 3, attaching it to another creature you control.
When Traveling Plague enters, Gremlin Tamer triggers, creating a creature token.
Activate Altar of Dementia by sacrificing the creature Traveling Plague is attached to.
When the creature dies, Traveling Plague triggers, returning itself from your graveyard to the battlefield attached to the token created in step 2.
When Traveling Plague enters, Gremlin Tamer triggers, creating a creature token.
Resolve the Altar of Dementia ability.
Repeat from step 3.
This fascinating loop turns a humble plague into an endless engine of sacrifice and resurrection. By casting Traveling Plague onto a creature and feeding that victim to Altar of Dementia, you trigger the Aura's inherent recursive nature—whenever the enchanted creature leaves the battlefield, Traveling Plague sneaks right back out of the graveyard to haunt a new target. Meanwhile, Gremlin Tamer watches each reincarnation with glee, its eerie ability generating a fresh 1/1 red Gremlin creature token every single time the Aura enters the battlefield to serve as the next sacrifice.