You control an Aura that is attached to another creature you control.
You control at least one additional creature beyond the creature that has the Aura attached.
Steps
Activate
Evereth by sacrificing another creature that has an Aura attached to it.
When the creature dies,
Cass triggers, returning an Aura that was attached to the creature from your graveyard to the battlefield attached to another creature you control.
When the Aura enters the battlefield,
Siona triggers, creating a creature token.
Resolve the
Evereth ability.
Repeat.
Notes
If you have a way to kill
Evereth and ({1} magic symbol) ({BR} magic symbol) available, you can do so after putting a significant amount of +1/+1 counters on it to deal damage to each opponent using its second ability.
Results
Infinite +1/+1 counters on a creature.
Infinite creature ETB.
Infinite creature LTB.
Infinite creature sacrifice triggers.
Infinite death triggers.
Infinite damage.
Metadata
In 0 decks according to EDHREC.
Bracket Tag
This combo has been estimated to be Exhibition (Bracket 1+).