A beholder's central lair is typically a large, spacious cavern with high ceilings, where it can attack without fear of closing to melee range. The cavern is unnaturally bright with vibrant colors and vivid patterns such as rainbows, clouds, and stars against bright backdrops. The designs seem to radiate light all their own, and everything in the lair is illuminated as if it were in direct sunlight, affecting creatures with Sunlight Sensitivity. A beholder encountered in its lair has a challenge rating of 15 (13,000 XP)

Lair Actions

When fighting inside its lair, a prismatic beholder can invoke the ambient magic to take lair actions. On initiative count 20 (losing initiative ties), the prismatic beholder can take one lair action to cause one of the following effects:

A colored wall of light--up to 60 feet long, 30 feet high, and 1 inch thick--appears within 120 feet of the prismatic beholder until it is destroyed. These walls amplify the effects of chromatic rays if a same-colored ray passes through a wall, but creatures and objects can pass through the walls freely and without penalty. Prismatic walls can cross, but cannot overlap.

The prismatic beholder can't repeat a color until they have all been used, and the color wall is destroyed. An antimagic field, including the prismatic beholder's antimagic cone, has no effect on the walls.