{Essence Backlash}
If there's an effect on the battlefield or say a card that gave your creatures +X/+X until end of turn (x being any number that the effects might give from 1 to infinite)
Does it increase power of creatures on the stack as well? Or is a creatures power on the stack only ever what is printed upon the card?
A cards power on the stack is as it is written on the card.
The only true exception to this are cards that have */* as their power and toughness which will always be what it should be, e.g {tarmogoyf} or {Lost Order of Jarkeld}