I have two actions that I want to do, one right after the other. I want to try to avoid anything happening between the two actions that could interfere with my plan.
What I want to do is, on one turn, Ready the first action with a trigger of "immediately before my next turn." (Or, equivalently, "at the end of the turn of the creature before me.") That way, right after my readied action goes off, it will be my turn again, and I can do my second action. Is this allowed?
Best Answer
No, you can't do that. Purely mechanical events like "at the end of my turn" or "before your turn" are not legal triggers (PHB, p. 193, emphasis mine):
That means that only things that your character could perceive make for legal triggers.
So, say we have two PCs Yolanda and Xavier, and Yolanda's turn comes after Xavier's.
Can Yolanda ready an action to be triggered by the end of Xavier's turn?
No, because a turn ending isn't a perceivable circumstance.
Can Yolanda ready an action to be triggered by Xavier's attack (or move, etc.) instead, to get the same effect as readying for “after Xavier's turn”?
The answer depends on the answer to “Is Xavier's activity perceivable?” If yes, then “Yes Yolanda can.” If no, then “No Yolanda can't.”