Toppling Spell (Metamagic)
Your spells with the force descriptor knock the affected creatures prone.
Benefit: The impact of your force spell is strong enough to knock the target prone. If the target takes damage, fails its saving throw, or is moved by your force spell, make a trip check against the target, using your caster level plus your casting ability score bonus (Wisdom for clerics, Intelligence for wizards, and so on). This does not provoke an attack of opportunity. If the check fails, the target cannot attempt to trip you or the force effect in response.
A toppling spell only affects spells with the force descriptor.
Level Increase: +1 (a toppling spell uses up a spell slot one level higher than the spell’s actual level.)
If I shoot 5 magic missiles because I'm CL 9+, and I target 5 separate creatures, does it trip all 5? It says if the target takes damage I get to make a trip attempt. Does Toppling apply to only one of those missiles, or all 5? Per RAW, I'm inclined to believe all 5 would cause trip.
You are correct.
Excellent feat.
I really like it with magical lineage (magic missile) trait to keep it a level one spell. On a Magus it's great because you can use your iterative attacks to trip people and use topping MM to down the rest in the same turn.