At least one Persist Creature has a +1/+1 counter on it.
Steps
Activate
Evereth by sacrificing the Persist Creature that has a +1/+1 counter on it.
When that creature dies, its persist ability and
Reyhan trigger.
Resolve
Reyhan's ability, putting at least two +1/+1 counters onto the surviving Persist Creature due to the counter-increasing effect.
If that creature had a -1/-1 counter on it, remove that and one of the +1/+1 counters from it as a state-based action.
Resolve the persist ability from step 2, returning the Persist Creature from your graveyard to the battlefield with a -1/-1 counter.
Resolve the
Evereth ability from step 1.
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 103 decks according to EDHREC.
Bracket Tag
This combo has been estimated to be Exhibition (Bracket 1+).