When a player leaves a multiplayer game, any continuous effects with durations that last until that player's next turn or until a specific point in that turn will last until that turn would have begun
I personally would rather have synergies with noncreature cards than five-color access, so Dynaheir is my pick but its truly a matter of preference
Heres a few I like, in no particular order
But the tactical change I think would could be benefit the deck is employing Eerie Interlude and Ghostway to blink our defenders in order to emulate Mind Spring at an advantageous point in the game and refill our hand
You may be thinking, "Wait, when Thoughtseize is played, it does the same thing every time: answers the most powerful card for one mana
Just recently, I ran into a game where, if Id actually been counting, Constant Mists had undoubtedly been cast at least twenty times