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 Umbral Collar Zealot 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 Umbral Collar Zealot ability.
Repeat from step 3.
This ingenious loop turns a creeping curse into an endless engine by exploiting Traveling Plague's clever recursive trigger when its host leaves the battlefield. By using Umbral Collar Zealot to sacrifice the enchanted creature on demand, you send the Aura to the graveyard only for it to immediately bounce right back onto a fresh target. Meanwhile, Gremlin Tamer watches eagerly, its eerie ability turning every single one of those ghostly re-entries into a brand-new Gremlin token that stands ready to be sacrificed next.