In Tales from the Yawning Portal (p. 209), in area 20 of the Hall of the Fire Giant King (in Chapter 6: Against the Giants), there's a variant drow elite warrior who is mentioned as a commander, and has three magic bolts. The text reads as follows:
[...] The commander has a +2 shortsword, a +1 hand crossbow, and three magic bolts, as follows:
- A bolt of holding, which casts hold person on a target hit with the bolt, as well as up to two other targets within 30 feet of that target
- A bolt of blinding, which casts blindness/deafness to blind on a target hit with the bolt, as well as up to two other targets within 30 feet of that target
- A bolt of vapors, which casts stinking cloud centered on the point it hits
Each of these effects has a spell save DC of 15 and a duration of 1 minute.
Does "casting" Hold Person and Stinking Cloud like this require the drow commander to maintain concentration on the spell?
It seems too powerful for a CR 5 creature to be able to paralyze three creatures in a single action without concentration.