The infestation effect is very in-flavour and interesting for a rat deck.

But I don't think it actually wants to be a keyword - both because it's a very narrow deck that would make use of it, and because multiple copies of the effect would rapidly become very very silly.

I conceived this set as wanting a lot of tokens between the four tribes. Rats got the best end of this stick, since their mechanic to generate tokens is easier than Hellions, and Dogs and Goblins didn't get mechanics to make tokens.

Most Infestation costs require two mana. This creature, Giant Rat, and Fixolya's Guard are the three whose cost is only one mana. While the other two were more expensive french vanilla, this was created to come onboard earlier.