Icicle Trap

2nd-Level Abjuration
Casting Time: 10 minutes
Range: 15 feet
Components: VSM (a shard of glass shaped like an icicle)
Duration: Until dispelled

When you cast this spell, you create a 10-foot square area of icicles on a ceiling, doorway, or similar overhang. The icicles fall when a creature walks beneath them. The creature must make a Dexterity saving throw. On a failure, the target takes 3d10 piercing damage, or have as much damage on a successful save. You can set conditions for creatures that don’t trigger the icicle trap, such as exempting yourself or those who say a certain password.
A successful Intelligence (Investigation) check against your spell save DC recognizes the icicles as dangerous and likely to fall. The icicles are destroyed if they take 15 points of fire damage.
At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d10 for each slot level above 2nd.

Source: Knuckleheads & Other Such Curiosities: A Travelers’ Guide to Icewind Dale