Epochrasite is a mensch. There are so many incidental ways to 'activate' it - Unearth/cheap reanimation, blink, Reveillark, early sac effects.
Perilous Myr is sweet.
Lightning Greaves never seems to be talked about given just how good it is. Maybe it's just taken for granted that it's insane, but then I rarely see it in lists.
O-Stone seems too clunky. Killing planeswalkers might be a good thing given how little of the old mass removal does (think Nev's Disk) but it makes it hard to abuse in a profitable way.
Needle is unremarkable but gets the job done.
Horn of Greed can't be good in Limited. Please prove me wrong on that if you can.
idk what to think about Scroll Rack. It looks good on paper but was terrible in practice for me.
Mimic Vat is great, include it right away.
Mindslaver is soooo expensive. It's only ever good if you have ways to cheat it out, though from what I've seen of your Cube the pace might be slow enough that it can compete on its own merits?
Mask of Memory is... eh. Aggro decks don't want it, so you're reduced to slapping it on a Vendilion Clique or something in your midrange deck. That's ok, but... eh.
Mortarpod is a necessary component of the sac/Zombie theme I imagine but it looks so unimpressive against any Baneslayer-esque card.
I like Prism! It's ideal for those of you who want colourless fixing but hate Signets/colourless accel
Sphere is playable but the possibility of it being dead offends me.
The only reaction you can really have to Clasp is 'play it if you have stuff it works with, don't otherwise'
Vault Skirge is also great with Pods and Devotion.