When the phrase of an effect states "Since your last turn". Does this also include the entire turn in which you took? It doesn't state "start" or "end" of your last turn, only "since" your last turn.

So for example...

Starro:
"At the beginning of your turn, if Starro took damage since your last turn, choose a friendly character with �(Starro's Minion)� in their name. This turn, that character has �FREE: Make an attack.�"

Agent May:
"THE CAVALRY: If another friendly character has taken damage since your last turn, Agent May can use Willpower."

Nightmask:
"ENERGY DISCHARGE: If Nightmask has taken damage since your last turn, modify his combat values by +1."

If you are pushing with willpower, taking mystics, colossal stamina, etc. Would that still count for it? Or does "Since" your last turn effectively mean since the end of your last turn?

I believe "since" here is being used as a preposition, and the definition for "since" as a preposition is given as follows in Merriam Webster online: So "in the period after [your last turn]" would be the right reading.

So if a friendly character takes mystics damage, or critically misses, then Agent May can use Willpower that same turn. She can't use it your next turn because it happened during your last turn, not since your last turn.

Since Starro checks at the beginning of your turn, he won't get to use his power based on taking damage during your turn from pushing, mystics, etc.

I would say "Since your last turn" would not include your last turn.

But that still leaves it open for damage taken during your current turn (except Starro who specifies "at the beginning of your turn", so the damage would have to occur during the begging of the turn phase)

Also, I'm no expert. Just my opinion

Also, most of this was already stated by ClixCommand3r.... may bad