Earthcraft is the best source of mana to fuel a number of infinite combos involving Doubling Season, Cathars Crusade, The Meathook Massacre, and Corpse Knight, among others, but these cards only scratch the surface of your combo potential with this commander, so if thats your preferred style of play, the linked primer above is going to be your best starting point for deck construction
This lets you create an exact copy of Pack Rat, copy ability included, for just three mana and a card from your hand, turning any late-game dead draws into more Rats for your swarm
When this creature dies, if it's not a token, create a token that's a copy of it, except it's an artifact in addition to its other types
The Dragon Whelp tokens produced are pretty potent in their own right and can threaten to close out a game