See the Unwritten
No preamble, I can't wait to launch into my spiel about this boner-inducer.
As much as I wasn't excited about Temur Ascendency for my Maelstrom Wanderer deck, this is an auto-include. You're triggering ferocious with this spell in that deck, so you're getting 2 creatures in the top 8 of your library when you cascade into this. Your deck is set up to get a lot of value and this is a great way to do it. While Summoning Trap was more flexible in its day, this is much better than trap in EDH, especially if you get to cast this for free, or copy it, or you're assured that the creatures you get are on the order of Deadeye Navigator and Prime Speaker Zegana rather than the Sylvan Caryatid and Elvish Mystic you have a decent shot of hitting in Standard.
Speaking of Standard, if we get bigger creatures than we're seeing right now, this could get there. It's pretty easy to trigger Ferocious from what we've seen so far, especially in Temur and Abzan, and old favorites like Polukranos, World Eater and Arbor Colossus can help out.
As sick as I am of hearing the phrase "Graveyard theme" from the mouths of people who wants to justify some of the things they said about the +1 ability on M15's Jace (forgetting that WotC admitted to doing next to no testing on JTMS' fateseal), it seems like Sultai is all-in on filling up the yard. This can take some of the sting out of getting pantsed by Tormod's Crypt or set you up to benefit from a big Delve. I think this is too clunky for Standard, but maybe the delve deck really wants to be 3 colors and run a 5 mana 4/4. I certainly like Ankle Shanker well enough. I don't see this being above $3-$5 best case scenario, though.
Flying Crane Technique
The real question is "Is this card better or worse than Draining Whelk?"
I actually don't know. It all really depends on whether the format will be slow enough for Morph to get there, I hope so, because every Morph creature so far is flipping up for 5-7 mana just about, and that's way slow. This is making me want to brew something with Ixidron and the pickles lock in EDH, especially since Deadeye Navigator makes the morph cost 1U. This is powerful, but if it's too slow, that might not matter.
Probably near-unbeatable in Limited, this could see some standard play. Broodmate Dragon was an excellent finisher in control decks and later in Jund and this does a decent approximation, with the added benefit of giving you non-trivial lifegain. Is it Baneslayer Angel? I am not convinced it is. It might, however, see some Standard play and that could give it significant upside. EDH likely doesn't have room for this.
Target Morph creature becomes a 4/4.
I don't know that this is playable out side of limited, nor do I know that it's not too narrow to play in every limited deck. This is likely a bulk rare unless I'm missing something pretty major. Germ tokens are black, Scuttling Doom Engine is big enough and Bronze Sable isn't in Khans of Tarkir boosters.