If you cast a spell that was countered, Nightpack Ambusher’s last ability doesn’t trigger.

Because damage remains marked on a creature until it’s removed as the turn ends, nonlethal damage dealt to other Wolves and Werewolves you control may become lethal if Nightpack Ambusher leaves the battlefield during that turn.

A creature that’s both a Wolf and a Werewolf gets only +1/+1 from Nightpack Ambusher’s ability.

Nightpack Ambusher looks at the entire turn to see if you have cast a spell, even if Nightpack Ambusher wasn’t on the battlefield when that spell was cast. Notably, you won’t get a Wolf token during your end step if you cast Nightpack Ambusher during your turn.