Gnarlback Rhino

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
Whenever you cast a spell that targets this creature, draw a card.

Pioneer Masters

"The bad news is the siege wall is gone. The good news I've got ideas for a new battering ram."
—Sergeant Ginnick

Foundations

"I think it's trying to tell us that the forest is angry."
—Vivien Reid

Double Masters 2022

Trample
Whenever you cast a spell that targets Gnarlback Rhino, draw a card.

Core Set 2020

Trample  (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
Whenever you cast a spell that targets Gnarlback Rhino, draw a card.

Gnarlback Rhino's last ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.

Gnarlback Rhino's last ability triggers when you cast a spell that has multiple targets as long as at least one of those targets is Gnarlback Rhino. It doesn't trigger multiple times if you cast a spell that targets Gnarlback Rhino multiple times.