Stocking the graveyard could be mere fuel for Varina, or it could provide an avenue for fueling powerful zombies and zombie-typal cards like Hashaton, Scarab's Fist, The Scarab God, and Gisa and Geralf
And an extra Gush will put you ahead by four cards for little to no mana
And, as with any card that doubles, Prodigy does have combo potential, though with how complex it can be to set these combos up, you might be better off just relying on the raw power of doubling specific abilities: 1
It won't be shuffled into its owner's library
Since Urborg, Tomb of Yawgmoth makes all lands into Swamps, so long as someone at the table has a copy in play, you can recur Bubbling Muck and untap lands as often as your cards will allow before casting a spell like Exsanguinate or Torment of Hailfire to win