I love this card's idea, it fits the Life element extremely well and the extra attacks also fits with Life abilities. However, since this is supposed to be used as CC in mono-Life or Life duo decks, I suggest the following change:
"This card attacks 1 extra time for every
![Life :life](https://elementscommunity.org/forum/Smileys/solosmileys/../../../images/Misc/life18x18.png)
creature that died this turn."
I believe it makes more sence this way and it prevents the OP usage with Sparks. As for the effect, it will be passive, it lasts until the end of turn and it is triggered every time a
![Life :life](https://elementscommunity.org/forum/Smileys/solosmileys/../../../images/Misc/life18x18.png)
creature's death effects are triggered.
Adrenaline won't help with Mother Bear's ability, since it won't attack 4x times per killed life creature, but it will attack 4x times (Adrenaline's buff) plus one more time per killed life creature.