I agree Day's Undoing is a good interaction for Brain in a Jar, however, it will not end your opponent's turn. The card checks if it is your turn, if so end it.
I have not tried it yet, going to tomorrow night. I see a lot of people running 1-2 Ulamog. I agree he is great. But I am going to try running 1 Mog and 1 Emrakul. I know he is more expensive but with Sower and the Eldrazi land he may be doable. Uncounterable with pseudo haste, cant be spot removaled, and take 6 things out. Just my logic.Emrakul, the Aeons Torn
Just brainstorming today, if you are in the pinch for life to sac him to Miren, the Moaning well, gain 15 life then possibly tutor him up again at the end of your opponents turn (If he didn't already win.)
12 Island
11 Swamp
Spells
4 Anticipate
2 Beck // Call
4 Brain in a Jar
2 Breaking // Entering
4 Day's Undoing
2 Far // Away
3 Inquisition of Kozilek
4 Remand
4 Serum Visions
2 Spell Pierce
2 Thoughtseize
2 Tezzeret the Seeker
Creatures
2 Spellskite
This is more of a fun modern deck with some get there fun.
I haven't even thought about the mana because it will probably be the same u/b mana base as all decks.
Just brainstorming today, if you are in the pinch for life to sac him to Miren, the Moaning well, gain 15 life then possibly tutor him up again at the end of your opponents turn (If he didn't already win.)