Thanks for the tips.
I had in fact considered the idea of reducing the swarm's HP, but I think I will solve it having the swarm act as reduced numbers until the start of the caster's next turn. This of course in case the Sleep spell doesn't affect the whole swarm.
Cheers,
Jorge
What happens if the swarm wants to move before the caster's next turn? I can think of a few ways of handling sleep.
1. Swarm as single creature: Sleep either works or it doesn't. Treat the swarm as a single creature of that hp for determining the effects of sleep and who gets affected.
2. Swarm as lots of groups of creatures of 1 hp each: A number of 1 hp groups of creatures equal to the sleep spell are affected first before other creatures.
In the case of #2 and the roll is less than the swarm's hp, you have to decide what to do with the swarm. I can think of a few options.
1. The activity of the swarm (essentially crawling all over each other) instantly wakes the rest of the swarm up at the start of its turn.
2. The activity of the swarm wakes up groups of creatures equal to the non asleep groups (20 hp swarm, 15 hp asleep, 5 hp awake, 10 hp awake at start of turn).
3. Swarm splits into asleep and awake swarms.
Myself, I would go with number 1 up top and treat it like another creature. D&D is not a simulation where everything has to perfectly match what you experience in real life, The normal rules are
usually good enough. That said, any of the other solutions would probably also be good enough, they just require more work and bookkeeping (although not too much).
Have fun squishing the bugs!
