My wizard recently acquired a Staff of Swarming Insects, and I used its Insect Plague spell for the first time. I cast it with the resulting sphere of locusts centered around my character, essentially acting as a (very effective) barrier against some powerful melee-based enemies.
The question came up afterwards, though, whether I used it correctly — as written, the spell damages "each creature" within the sphere, which would technically include my own character. We noticed this because one of the staff's other spells (Insect Cloud) creates a similar but non-damaging effect but specifically states that its effect applies to creatures other than you, something I'd assumed was inherent in these types of spells that give the player control over some type of focused effect.
So is the Insect Plague spell really only useful focused somewhere away from the player character (to avoid damaging themselves), or is the spell's wording just somewhat ambiguous?