Discard a Mountain to the Rats. Also, I've put the previously-discarded Forest in my Graveyard.
Untap, upkeep, draw.
Mountain.
Level up twice.
Attack with Beastbreaker (no assumed blocks this time).
Blocks/responses?
Turgy22: 12
Hand: 3
Library: 28
Battlefield:
(TT) Swamp x2
(TTT) Island x3
(T) Seafloor Debris (Seafloor Debris enters the battlefield tapped; T: Add U; T,Sac: Add one mana of any color to your mana pool.)
(S) Ravenous Rats (1/1; Rat; When Ravenous Rats enters the battlefield, target opponent discards a card.)
(S) Gravedigger (2/2; Zombie; When Gravedigger enters the battlefield, you may return target creature card from your graveyard to your hand.)
Graveyard: Cancel
Exile:
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rokapoke: 20
Hand: 2
Library: 28
Battlefield:
(TTTT) Mountain x4
(TT) Forest x2
(T) Beastbreaker of Bala Ged (6/6 Trample; Human Warrior; Level Up 2G; Level 1-3 4/4; Level 4+ 6/6 Trample) Level 4
Graveyard: Mudbrawler Raiders, Forest, Mountain
Exile: