Useless Blue Spells
1: Disrupting Shoal is going to be the main reaction card in the deck. We have a great cmc curve for it, and will usually be able to mess up the opponent's strategy in the early game. Late game, we can just hard cast it and we don't have to worry as much about running out of steam.
2: Commandeer is just an absolute unit. We only play one because of how taxing it is. Against tron decks that run karn, jund decks that run liliana, and basically any deck that has a really good noncreature spell, this card can win games.
3: Force of Negation was printed right after Narset, Parter of Veils, and is yet another buff to an already OP deck. If we don't have commandeer, this is your best second bet.
4: Snapback is a super useful card to have in the deck because it is something that we can cast for free during an opponent's turn (to remove counters from titi) which will almost always have a target. You want to get to your upkeep on turn three with as few counters on titi as possible, and snapback will get you there.
5: Cryptic Command is the staple mono-blue card. We will usually be using it tap down creatures so we can buy time before Thing in the Ice
flips, but the counter magic is useful as well.
6: Spell Pierce/Spell Snare are the key one-drop counterspells, curving out the deck fro disrupting shoal and providing early responses. These should be used on anything they can target, and are mainly used to stall out until you can get the real counter magic going.
7: Remand, Unsubstantiate, and Mana Leak fill the 2 cmc slot, and are again mainly used to stall out the game. Remand and unsub can be an especially detrimental tempo play against some combo decks.
8: Engulf the Shore is key against most creature decks if we don't have thing in the ice in play. Unless you're hitting a hogaak deck, you should be able to bounce all their stuff
9: Commit / Memory is an amazing dual nature card in this deck, providing early protection and late game cycling as an extra (expensive) copy of Day's Undoing.
10: Opt is unimportant
The Combo Pieces
1: The deck is built around Narset, Parter of Veils. She is the main lock piece in tandem with the cycle and loot effects.
2: Day's Undoing is an amazing card, locking the opponent out of the game in one go with narset and refilling the hand for your pitch spells.
3: Thing in the Ice
is the main win condition, and he lets you basically play a one-sided karn ultimate when you have narset in play and a cycle effect in hand. They get to keep their lands, but whatever.
4: Geier Reach Sanitarium and Lore Broker keep the opponent locked down after a good Day's Undoing by denying their draw. If you loot on their upkeep, with narset on the field, they can't draw during their draw step, leaving you free to swing in with your 7/8 Awoken Horrors.