Activate Necrotic Ooze using Garth One-Eye's ability by tapping it, causing you to pay ({0} magic symbol) to cast a copy of Black Lotus.
Activate Black Lotus by tapping and sacrificing it, adding ({G} magic symbol) ({G} magic symbol) ({G} magic symbol) .
Activate Necrotic Ooze using Barrenton Medic's second ability by putting a -1/-1 counter on it, untapping it.
Activate Necrotic Ooze using Garth One-Eye's ability by tapping it, causing you to pay ({1} magic symbol) ({G} magic symbol) to cast a copy of Regrowth.
Resolve Regrowth, returning Garth One-Eye to your hand from your graveyard.
Activate Necrotic Ooze using Krosan Archer's ability by paying ({G} magic symbol) and discarding Garth One-Eye, giving Necrotic Ooze +0/+2 until end of turn.
Activate Necrotic Ooze using Barrenton Medic's second ability by putting a -1/-1 counter on it, untapping it.