Sorry, I guess should have read 'When Slow Drops'... That being said...

So, this was a weird one that came up this afternoon. The boys were sandboxing against a Beholder to get back into the swing of things. The party's wizard had cast Slow on a couple of goblins and the Beholder. Two or three turns later, the Beholder casts its Sleep ray on the wizard. Its turn went like this. It flew up ten feet and then cast Sleep. The wizard fell down asleep.

So, not sure how to handle this one. This is what I did. Since the wizard was asleep, Slow was dropped. Is that right? And since it was dropped I allowed the Beholder to take the second half of it's movement (fly 20 ft) on that same turn instead of waiting until it's next turn. Was that right?

If a caster goes to sleep, does any lasting effect spell drop? And if so, does the target get back everything immediately of which it was prevented from doing?

Thanks all.

Slow is concentration, so as soon as he goes to sleep he's no longer able to hold concentration on the spell, so it definitely drops.  I would rule that as soon as concentration dropped, slow was no longer in effect.  As for the second part, I think you did it right.  I see no reason why the movement would not be available the moment that the slow dropped.

Thanks Hawk. Just what I was thinking. I would like further confirmation on the second part specifically. But, yeah, in the moment, made perfect sense.

Yes, it loses the restrictions of the spell when concentration is broken. So it already moved 10 feet and now its total allowed speed is back to 20 feet, so it can move 10 more before the end of its turn.