If {Ageless Entity} were to be given lifelink and attack a 4/4 creature. Would you be able to save it by gaining the life and putting the counters on as a result of the battle damage it deals?
I don't believe so- the counter ability is triggered, so that would have to resolve first.
Awe alright. I was thinking it'd die first then the counters would go to be put on it and disappear but was hoping I was wrong.
The important things to remember are that combat damage all happens at once (except for first/double strike) and that combat damage doesn't use the stack. So if Ageless blocks a 4/4, all that damage is dealt simultaneously (both creatures die and you gain 4 life, state-based actions that don't use the stack, all before Ageless' lifegain>counters trigger can even be put on the stack.)