There are, of course, a number of smaller underlings in the brood, but most players are familiar with the hulking tentacled titans that often end games of Commander, whether through the annihilator mechanic or just by being really, really big
The four decks are largely creature based and when played together create a fun pod thats interactive and dynamic
Impact Tremors cannot damage creatures or planeswalkers, but Goblin decks are adept at pushing enough damage so effects like this can finish off the opponent sooner than later
Finally, you can spend 9 loyalty to activate: If target player has fewer than nine poison counters, they get a number of poison counters equal to the difference. All you have to do then is add another poison counter somehow - say, by proliferating - and that opponent is dead
Inevitably, there is someone out there who has played with that card as part of their decks engine and will defend that card to their death