Ashnod's Altar | Herd Baloth | Host of the Hereafter (and one other card)

Gives +1/+1 counter to creatures that enter

Cards

Cast
Herd Baloth by paying its mana cost.
When
Herd Baloth enters, the effect that adds +1/+1 counters to entering creatures triggers or applies its replacement effect, putting at least one +1/+1 counter on
Herd Baloth.
Herd Baloth triggers, creating a creature token.
When the creature token enters, that same effect causes you to place at least one +1/+1 counter on it.
Activate
Ashnod's Altar by sacrificing the creature token, adding ({C} magic symbol) ({C} magic symbol) .
When the creature token dies,
Host of the Hereafter triggers, putting at least one +1/+1 counter on
Herd Baloth.
Repeat steps 3 and 4 once.
Repeat from step 5.

This combo has been estimated to be Exhibition (Bracket 1+).