Does the spell slow stop this?

[Sir cryosin]

Can the spell slow stop monster from taking lair and legendary actions?

[TurboGhast]

RAW, Slow doesn't stop any legendary actions. I'm okay with this, because monsters with legendary actions seem designed to threaten the PCs alone, and having a spell that's a save or suck than can trivalize the most threatening monsters at a low enough spell level that it can be easily spammed seems extremely unbalanced.

Edit: Fixed some wording awkwardness is the above sentence. Also, I'd be perfectly okay if PC abilities never specifically interacted with legendary and lair actions, since those are rare and very high level.

[Erys]

Slow will also not affect lair actions.