Like all the team up cards from March of the Machine , Borborygmos and Fblthp have a mashup up of abilities from Fblthp, the Lost and a slightly nerfed pitch-lands-for-damage ability from Borborygmos Enraged
Triggers like this one go off from the battlefield, not from the graveyard
Along with that, it also has Vigilance, Trample and Haste - which means it can not only attack the turn it comes in, but also defend even if it does attack
I've actually felt an absence of johnny cards in my last draft
For each of them, exile the top card of your library, then Soulfire Eruption deals damage equal to that card's mana value to that permanent or player
It gets better as targetted discard gets worse