I'm so glad Polymorphist's Jest is getting the love it deserves. Also holy shit a solid $2 deck. I'd add some scry temples though (specifically, Temple of Deceit and Temple of Epiphany ) and also mainboard Scouring Sands as it is a total board wipe and can pave the way for your own attack (I'd take out two Stormtide Leviathans and put in 2 Sands, simply because Grixis doesn't play enough ramp to justify having a lot of 8-drops in a deck and you'll be playing some scry anyways so you have a bit of future sight.) +1 nonetheless.

@hahaha69lmao: I'll have to fine-tune the number of fatties after getting this together and playtesting. My worry with having only one is that if I draw it, I don't have something like Footbottom Feast to get it back into my library so I can get it out for 2U with Jalira.

Temples would fit in really well here, though, and I do need a little extra scry.

Glacial Crasher would be better than that Nightfire Giant.

I'd recommend using some cards from theros. Using big powerhouses

Actually I just noticed Festergloom is a sorcery. In that case I'd definitely replace it with Scouring Sands on the SB as you can have your boardwipe for five mana instead of six.