Gwenna by tapping it, adding ({G} magic symbol) ({G} magic symbol) that can only be spent to cast creature spells or to activate abilities of creatures.
Cast
Ghalta by paying ({G} magic symbol) ({G} magic symbol) .
Brinelin and
Gwenna trigger.
Resolve the
Brinelin trigger, returning
Thrasta from the battlefield to your hand.
Resolve the
Gwenna trigger, putting a +1/+1 counter on it and untapping it.
Activate
Gwenna by tapping it, adding ({G} magic symbol) ({G} magic symbol) that can only be spent to cast creature spells or to activate abilities of creatures.
Cast
Thrasta by paying ({G} magic symbol) ({G} magic symbol) .
Brinelin and
Gwenna trigger.
Resolve the
Brinelin trigger, returning
Ghalta from the battlefield to your hand.
Resolve the
Gwenna trigger, putting a +1/+1 counter on it and untapping it.
Repeat.
Notes
You can start the combo at lower storm counts if you can pay for
Thrasta until your storm count reaches 4 when you cast it.
Results
Infinite +1/+1 counters on a creature.
Infinite ETB.
Infinite LTB.
Infinite storm count.
Metadata
In 505 decks according to EDHREC.
Bracket Tag
This combo has been estimated to be Exhibition (Bracket 1+).