Wanted to build the new Thassa as soon as I saw her spoiled. Finally got all the pieces to finish it in paper.
This deck is mostly about being a huge ETB value engine. Get Thassa out, then start flickering things. Early/mid game you can drop down things that don't seem like major threats on their own, until you realize that recurring their ETB triggers gets you a TON of mileage. Late game you can completely take control or combo out mercilessly. There's also a wizard subtheme, which is fun.
Some fun things:
Panharmonicon + Agent of Treachery + Thassa, Deep-Dwelling 4 steals per turn. Even more if you can sneak in a couple with Deadeye Navigator. This same synergy applies with Venser, Shaper Savant, except instead of stealing things you're essentially capsizing them. 4+ permanents back to hand per turn is nothing to scoff at.
Chamber of Manipulation or Sower of Temptation or Callous Oppressor or Vedalken Shackles (you get the idea. Steal something) plus Thassa, Deep-Dwelling means you get to steal something indefinitely. Grab something "until the end of turn" then flicker it, it becomes yours permanently. Then you can use those stealy things again, since they're not bounded to the stolen creature anymore.
Glen Elendra Archmage + Thassa, Deep-Dwelling. If you flicker her, she comes back without a counter, letting her persist much more. That's a lot of countermagic.
Solemn Simulacrum + Thassa, Deep-Dwelling. This boi is crazy. The deck runs a ton of basics. Can get him out as early as turn 2 then, once again through the wonders of flickering, just accelerate at speeds that might seem ludicrous for a blue deck.
Verity Circle + Thassa, Deep-Dwelling is an excellent card drawing engine which can come in clutch late game. It's a little expensive but it's just added value since you're going to try to lock down threats anyways. Throw in Training Grounds and it almost looks efficient.
Less fun things:
the game has to end eventually, and here's some ways to do it if you're not having enough fun just taking everyone's things and drawing a bunch of cards.
Palinchron gives you infinite mana with High Tide or Caged Sun or Deadeye Navigator or Gauntlet of Power. Peregrine Drake + Deadeye Navigator is also a decent alternative outlet. Once you have infinite mana, you can Capsize everything that's not yours and take the win. Or you can Blue Sun's Zenith yourself to draw your deck and throw down Thassa's Oracle. You can also blue sun's other people to death, which can be fun.
Archaeomancer or Spellseeker plus either Time Warp or Capture of Jingzhou nets you infinite turns with Thassa out. Play the extra turn spell or simply have it in your yard, play the wizard (or already have them out) then flicker them end of turn to get the extra turn spell back. Play it, repeat.
Windfall + Narset, Parter of Veils. This doesn't win the game by itself, but it is funny/ Kinda a one sided Timetwister.
Omniscience kinda says "I win the game" as long as you have either cards in hand or way to draw them. It's not too hard to get the mana to play it, and can be a nice thing to dump extra mana into. Even if it doesn't stick around for long, if it lands at all it can put you extremely far ahead.
Some considerations:
So far in pods this deck is 7-2. One game loss was after keeping a 2 land hand and not drawing into anything the whole game. The other the table got combo'd out by fish hulk on turn 2 with no answers. Joy. The games I did win pretty much went as planned. It feels like you just kinda sit back and get a bit of value early on. The deck doesn't look like it's doing all that much early on, and your board state doesn't usually appear too threatening. People might ping you or swing low at you, but it doesn't appear like a problem outright until it's too late. It might look like you're durdling, then you just explode.
Frost Titan is a little weak (albeit fun). I think I might replace it with Rishadan Footpad or one of the others with the same effect. I could even run all 3, but they seemed a little overcosted and too threatening for the value they provide. I'll have to test them out. I might replace Force of Negation with Pact of Negation. The deck doesn't usually care that much about defensive countermagic. The countermagic it runs is used to either go off, or to counter really big threats or stuff that could keep us from going off. I could cut something else and run both, but as of now it's not too counterheavy and I kind of like it that way. I wanna be the blue player drawing a ton of cards, not the one countering everything in sight.
I'm open to other suggestions/cuts and general critique. I hope u like my fish.
