**Note to self: add more creatures with flash...?  Swap in Lord of the Forsaken for something else.  Also add in Infernal Darkness.  Maybe add The Golden Throne too?  Consider adding Vogar, Necropolis Tyrant.  Add Jar of Eyeballs: use once you have more counters than cards in your library, then rearrange your library in any order.

This is a pretty straightforward deck design... cast creatures, make creature tokens, sac creature tokens.  Free and reusable sac outlets are a must, but a few reusable 1 mana cost outlets are very worthy, plus a few that tap and sac.  But being able to sac creature tokens before casting a creature is a necessary element of the deck, as we obviously never (almost never) want to have 7+ thrulls in play (token or nontoken).  As such, only two creatures in the deck cost more than 6cc to cast... Reiver Demon is too strong to leave out, and Razaketh, the Foulblooded can immediately tutor a grave recursion spell to put Endrek back into play.  Unless a sac effect is needed, it probably makes sense to try and only sac creature tokens right before casting a new creature.

I settled on 13 nonland draw cards (plus two land options), only one of which is a single use spell, and this includes Razaketh for tutoring, and Bolas's Citadel for playing cards off the top of your library, which IMHO are as good as or better than normal card draw.  In terms of draw potential per turn, I categorize three cards as small draw, three as medium draw, and seven as big/mass draw.  You could probably justify taking one or two out, but I've yet to playtest this deck, sooo....

Wake the Dead is a fun card in any aristocrats deck... bringing back creature cards that trigger on creature deaths (i.e. Zulaport Cutthroat, etc) when you're going to be blocking with and losing a bunch of creatures can be both very unexpected by your opponents, as well as very devastating.  Maybe bring back Krav, the Unredeemed in the mix, then sac all the creatures you block with that will die.  Or bring back Mikaeus, the Unhallowed, and bring those sacrificed creatures right back.  Lots of fun things Wake the Dead allows you to do in response to an all-out attack.

It's tempting to add Thrull Champion to boost your other Thrull tokens, or maybe add Thrull Wizard to keep with a Thrull theme, except that Endrek counts Thrulls, and we really don't want more than he creates, since the deck has been sculpted to have almost no creatures with a casting cost over 6.  My three exceptions are Razaketh, the Foulblooded, because he can immediately tutor a recursion spell to get your commander back from the graveyard; Reiver Demon, because you're wiping out everyone else's creatures; and Sheoldred, Whispering One, for the same reasons as Razaketh (bring back Endrek the next turn), except I ended up cutting Sheoldred out (but still want to put it back in).  On that note, if you are including enough recursion (and why wouldn't you in a mono-black sac deck?), there's usually a reason in your hand or on the board to have Endrek go to your graveyard instead of the command zone when he dies, bringing him back with ease, and no commander tax issues.

Feaster of Fools can also be fun, especially if you have some recursion cards on tap to bring Endrek back from your grave... cast Feaster of Fools when you have six Thrull tokens in play, tapping four of them to convoke Feaster of Fools, and then creating six more Thrulls, then sac all 12 Thrulls to put 24x +1/+1 counters on Feaster, giving you a 27/27 flyer for two black mana.  Tar Fiend operates on Devour as well, but it's important to remember that the devour machanic triggers on ETB, not cast, so your opponents have to decide if they are going to counter it before you decide how many creatures get devoured and more importantly before you decide who will be discarding cards, making it less likely to get countered if your choice is not already obvious.  But, like with Feaster of Fools, if needed you can stack up 12 Thrulls and devour them all (forcing you to sacrifice Endrek as well), forcing an opponent to discard 12 cards and you get a 28/28 thumper, for 6cc.  These guys are kinda neato with Endrek.

Akroma's Memorial is tempting to put into any deck that's heavy on creatures, buuuut it makes all your creatures pro-black which means you can no longer target your own creatures, which makes it very hard to sacrifice them.  Alas, no Akroma's Memorial...

Krav, the Unredeemed has pretty obvious value here... only cost 1cc to use, doesn't tap, sac x creatures, draw X cards, gain X life, get X +1/+1 counters... it's pure goodness and value, when sac fodder creatures are so easy to come by.  Plus you can use him the turn he comes out, for 6cc total, and he'll be creating five creatures with Endrek that he can immediately sac.  And once enough land/ramp is available, you can use him multiple times per turn, after each creature cast... if you want.