Nagpa Reference (MPMM)
Legendary Actions
The Unburdened can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The Unburdened regains spent legendary actions at the start of its turn.
Attack. The Unburdened makes one attack with its Staff or Deathly Ray.
Spellcasting (Costs 2 Actions). The Unburdened uses Corruption, Paralysis, or Spellcasting.
Lair Actions
On initiative count 20 (losing initiative ties), the Unburdened takes a lair action to cause one of the following effects; the Unburdened can't use the same effect two rounds in a row:- Each creature in the Archive which failed the save of the Archway of Doubt is subjected to an Enemies Abound spell.
- Until initiative count 20 on the next round, any creature that tries to cast a spell of 4th level or lower in the Archive is wracked with pain. The creature can choose another action, but if it tries to cast the spell, it must make a DC 16 Constitution saving throw. On a failed save, it takes 1d6 necrotic damage per level of the spell, and the spell has no effect and is wasted.