Love It. +1 from me

maybe add a void winnower side/main board to control your opponents a bit more

I'm liking it! I wouldn't mind seeing more ingest though for all the processing you wanna do. I'd like bringing Fathom Feeder to the main as they probably don't want to block that, so you either ingest and draw cards or trade with a threat! Wasteland Strangler is also ultra sick, wouldn't mind seeing him in the main either.

Also Blight Herder I feel is an honorable mention as it can help get to an ulamog or just have chump blockers or allow you to go wide or some other things, very versatile but yes a big processing cost.

The reason Fathom Feeder is in the side is because it's the sexiest blocker i have in the deck, more or less. I've found running Mist Intruder is basically free ingest post turn 2, but if they have big creatures to deal with and/or I'm having late game drawing issues then they hit the main.

In terms of Wasteland Strangler, I love it too! Though my main deck is a little more directed towards control through exile counters and exile kills, I have found that this bad boy is more circumstantial but a definite necessity.

Blight Herder is beautiful, but I have it being put to better use in a different deck. Thank you for the feedback, it's always appreciated! :)

I'm curious to see how your deck will turn out. I may change my U/R eldrazi deck I'm working on into it, if your deck can survive early game U/R prowess decks.

I haven't tested it against u/r prowess yet but I'd switch out Forerunner of Slaughter for Fathom Feeder to counteract the prowess trigger of ground attackers, saving my Titan's Presence, Brutal Expulsion, and Oblivion Strike for flyers. Kozilek's Return is also available in the side if I need to go a more one turn wipe situation vs aggro. It seems to have the tools available, I look forward to finding out if it can hold its own.

Why no basic lands?

Honestly, I really only need one of each color on the field so I went about the best way to get them there. With basic lands I run the risk of not getting one of those colors when I really need it, if I'm drawing poorly. Thankfully it's a control deck, so I typically play slow and remain unaffected by the taplands!

I'd replace Ulamog's Despoiler with Conduit of Ruin. It doesn't need any cards in exile, can search for your singleton copy of Ulamog, and make creatures cheaper. Warping Wail is great utility that's even seeing Modern play. Flaying Tendrils good to side against Aggro, Rally, tokens and Prowess decks.

I like Conduit of Ruin a lot, he's in another deck I have but if I get Ulamog's Despoiler onto the field the game's basically over. I've never had a problem getting him out as a 9/9, given all the exile I have. For some reason I hadn't considered Flaying Tendrils, I have Kozilek's Return but the added bonus of exile from Flaying is probably better overall... I'll try to find space somehow lol

Eldrazi Mimic?

There was a point I was trying to fit Eldrazi Mimic in, especially for when I drop Ulamog's Despoiler but I need my ingest creatures and Forerunner of Slaughter just seems to be exponentially better fit. Further play and testing may change that though!

Interesting. Suggest taking away khans and fate reforged since they wont really be standard legal anymore.

Since Tomb of the Spirit Dragon works so well in this deck, I'm more or less stalling until the last possible minute to do that lol

Playing a deck very similar to this. Having a hard time against control decks. Planar Outburst is a terribly annoying card. Runs out of steam and Titan's Presence becomes almost useless. Definitely going to look into getting some Eldrazi Obligators, though.

I find whichever deck I'm playing against changes the tempo at which I play. Unless it's an aggro deck I typically keep 3 mana open on each turn with either Void Shatter or Spell Shrivel (or both) in my hand just waiting for them to do that. Even Brutal Expulsion can help to bounce the card back to its owners hand, and then there's always Ulamog's Nullifier if you've gotten enough cards into their exile pile!

Kozilek's return is way better b.c it's an instant. Wait until they cast a haste creature or a hordeling outburst before combat triggering prowess and u kill them all instead of what was already on the field during your turn. U also get to save for counters b.c it's an instant in case they play a planeswalker or something with higher than 2 toughness. It's also better b.c it can happen twice and the 2nd time it's for 5. The mana intensity is less as well which makes it easy to play early. Tendrils is good but there's a reason kozilek's return costs more than kozilek himself.

At least it did lol it's still $14 though.

What you said makes 100% sense, I'll switch out one of the Flaying Tendrils for a Kozilek's Return, the instant speed and basically free sorcery speed flashback is definitely worth it... I'm still feeling this deck out and trying to tweak it so thank you for the suggestion :)