1a. Is the Mayuri guardians effect a trigger effect? If it is, say your opponent attacks with the Mayuri - Squad 12 Captain, you play a card to negate trigger effects, would your oppenent indeed lose the game?
1b. Same situation, although you are only at 9 power or less, would you still win because any time you deal power damage with Mayuri you would lose the game, or does the life loss take precedent and the game ends before the effect goes off, or does it result in a draw?
2. I pay 2 souls to remove a character with sawatori guardian card effect. when that character comes back into play at the end of the turn, could I Dark Ritual that character to prevent it from coming back into play.
Answers:
1a and 1b. Nope. His effect replaces power damage to card discards, it's a constant effect.
2. No, the character isn't being played, he's being put into play by Sawatari's effect.