I have magic missile with caster level 3 and the toppling spells feat.
Magic missile says:
For every two caster levels beyond 1st, you gain an additional missile – two at 3rd level, three at 5th, four at 7th, and the maximum of five missiles at 9th level or higher. If you shoot multiple missiles, you can have them strike a single creature or several creatures. A single missile can strike only one creature. You must designate targets before you check for spell resistance or roll damage.
Toppling Spell says:
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.
So 1 missile, 1 target…simple. 1 trip attempt.
But I'm CL3, so I get to fire 2 missiles.
2 missiles, 2 targets…seems pretty simple, 1 trip attempt on each.
But I can fire both missiles at one target.
Magic Missile explicitly says that it creates additional missiles, not just increasing the damage from a single missile, so it's hitting the target multiple times. However Toppling Spell is talking about the spell.
So do I get 2 trip attempts or 1 when I fire both missiles at a single target?
Best Answer
By RAW there is no way to answer this for sure, magic missile does say it generates multiple missiles but this seems to be flavour rather than mechanical.
The key part I'm relying on in this answer is in the description of toppling spell: your force spell [snip] If the target takes damage
This clearly says that if the spell deals damage to the target then you get a trip attempt. It does not say anything about damaging the target multiple times, it just says that if the spell deals damage.
Based on this part of the rules the way I've been using the spell is to say that you get a trip attempt against each target struck by the spell that you deal damage to no matter how many missiles you hit that target with. If you hit three targets you get three trip attempts (one on each). If you hit one target three times you get a single trip attempt.
I'm aware of the sneak attack/rays FAQ but it's speaking about a completely different ability and a completely different style of spell so I do not see how it applies.