Mesmeric Orb is pretty much the quirkiest, easily-playable buildaround in my list, and it's loads of fun. It's colourless, so that's obviously a huge boon, and being
means you can run it out fairly easily at any time. There are a few scenarios to consider it for, though there's a lot of overlap among them and the list is by no means exhaustive.
- Control-Mill: This is the purest and most wild version of the deck. Here, you're looking for additional effects to force draws, mill extra, and tap-down, as well as board clog effects like Whirler Rogue and Meloku the Clouded Mirror. There's a lot of tools I've tried on and off over the ages, dialing back down and back up as the strategy intrigues me. Good enablers for mill include Dakra Mystic, Mindshrieker, Altar of Dementia, Reforge the Soul, Magus of the Wheel, and, typically, running a few extra cards in your deck as some extra-super-sneaky tech; even like 3 more cards can help a lot imho (but no more than 5 extra, you still need to draw into your mill!)
- Living Death/reanimator: less combo win, more value win. This one can get much more complex and would really like for tools to make sure that your reanimated board is best if you're using Living Death, and can sometimes wind up being more of a straightforward reanimator package, though things like Deathrite Shaman, Scavenging Ooze, and Mardu Woe-Reaper can help keep opposing 'yards in check while still being very cube-worthy includes
- Aggro-Mill: This is a deck I'd like to feature here in my discussion, because it's kind of a quirky brew and I'm not sure if it's a very obvious possibility. The angle of this deck is to drop the Orb as part of a low-curve deck, and if your opponent is midrange/control, they're gonna get wrecked just by trying to commit to the board or remove your paltry threats. Versus control, their usual cadre of draw spells works against them quite wickedly, which makes the Orb worth saving and dropping a bit late sometimes. A nice tutor effect helps the aggro version of this deck a lot; the point here though is that the mill win is primarily an alternative, rather than necessarily the top plan. Think of it like a cool, anxiety-inducing Devil's Play for guaranteeing you can go the distance if you get stumbled, except your opponent will likely misplay themselves into the loss rather than eating it out of nowhere.
These are just a few highlights; the card can do a lot, and needs exploring in your own format to work out. Often, the correct answer can be to just ignore it or race it if the deck isn't built to maximize on it, but most players don't realize that and start
FREAKING OUT and playing terribly, which is hilarious and really fun. Usual mill caveat to consider as part of this whole discussion is some people get really whiny facing against mill and you may need to get less boring friends consider how this will translate to mill being present in your format.
Re:
Sphinx's Tutelage, if you want a 1-card quirk-piece for blue control/durdle wins, I prefer
Increasing Confusion, which takes longer to start happening but cleans up the match quick. Also works just fine with draw-more effects like
Magus of the Wheel for accelerating the win/digging for the card itself, and ties into graveyard strategies, if you're dead-serious about them.
Aside from that, if you're looking for a U/R identity, I'll echo other comments that suggest a Spells-Matter theme. I've tried a very gentle form of storm before in my cube that was mostly URg, and I wasn't super impressed, though it was "neat" for a few drafts. UR artifacts is also a popular idea, although imho it lacks enough incentives in most cubes, as
Goblin Welder does not a 2-colour theme make (though it does provide a cool, fun deck). U-centered artifact interactions has been fun (note that I've only got like 3 blue cards in my list which feed into this, noting, again, it's sort of thin unless you want to get really poisonous...), but that's another tale for another time. For UR, I'd look at things like...
Flashback spells help push it and are also quite playable. The theme overlaps into white very well, but that actually just makes it a
better theme for being flexible.