Whenever another creature you control dies, if it had a +1/+1 counter on it, put a +1/+1 counter on Grakmaw.
When Grakmaw dies, create an X/X black and green Hydra creature token, where X is the number of +1/+1 counters on Grakmaw.
Grakmaw is a BG +1/+1 counters aristocrats commander: load up creatures with counters, sacrifice them for value, and grow Grakmaw whenever a counter-bearing creature dies. When Grakmaw eventually dies it leaves behind a huge Hydra, so it's resilient and self-perpetuating. You grind value through proliferate, sac outlets, and counter synergies until you assemble a big board or a combo finish.
Built-in resilience: dies into a large Hydra token, so removal rarely sets you back fully
Deep synergy with the strong BG +1/+1 counters and proliferate package
Aristocrats angle gives reliable value engines and incremental advantage
Low mana value (3) makes it easy to recast and abuse sacrifice loops
Counter synergies are fragile to board wipes and exile-based removal
Relies on enablers; a slow start without counters or sac outlets stalls
Grakmaw itself is small unless counters accumulate, so it's a poor early attacker
No card advantage built into the command zone beyond the death trigger
Legendary Creature — Hydra Horror
