One of my players is constantly bugging me about using Enlarge/Reduce to reduce a boulder to a smaller size and then hurl it via the spell Catapult, cancel the concentration on Enlarge/Reduce before the impact, and let the enemy be smashed by a much bigger one.
Can the Enlarge/Reduce and Catapult spells be combined in this way?
Best Answer
Yes this will work, but...
First off, Enlarge/Reduce can certainly make boulders smaller:
However, these boulders have to meet the requirements below for Catapult to shoot them:
So, you're looking at a boulder that is at most 40 pounds in weight. How big is that? I don't make a habit of wandering around the countryside weighing rocks, but if I had to guess I'd say probably a little bigger than your head. So far, we're good to go...
HOWEVER...
D&D 5e doesn't make rules to handle things like mass, inertia, coefficients of drag, and muzzle velocity...so all we're left with is the actual spell description. And, according to the Catapult spell:
So, yes you can totally Reduce a boulder to a size that the Catapult spell will work on it, and yes you can even drop concentration after it is shot toward a target, but the spell does 3d8 bludgeoning damage. Period.
The damage comes from the spell, not from what you use as the projectile. You can use a pound of soft butter, 3d8 damage. A pound of feathers, 3d8 damage. You can Reduce a boulder, 3d8 damage.