Expedition: White Plume Mountain

Water Breathing: The octopus can breathe only underwater.
Hold Breath: While out of water, the octopus can hold its breath for 1 hour.
Tentacles:Melee Weapon Attack: +5 to hit, reach 15 ft., one target.
Hit: 2d6+3 bludgeoning damage. If the target is a creature, it is grappled (escape DC 16). Until this grapple ends, the target is restrained, and the octopus can't use its tentacles on another target.

Bonus action to cast Shield of Faith for +2 AC, bringing it to 18.

Moonbeam
2nd-level evocation
Casting Time: 1 action
Range: 120 feet
Components: V, S, M (several seeds of any moonseed plant and a piece of opalescent feldspar)
Duration: Concentration, up to 1 minute
A silvery beam of pale light shines down in a 5-foot radius, 40-foot-high cylinder centered on a point within range. Until the spell ends, dim light fills the cylinder.
When a creature enters the spell’s area for the first time on a turn or starts its turn there, it is engulfed
in ghostly flames that cause searing pain, and it must make a Constitution saving throw. It takes 2d10 radiant damage on a failed save, or half as much damage on a
successful one.
A shapechanger makes its saving throw with
disadvantage. If it fails, it also instantly reverts to its
original form and can’t assume a different form until it
leaves the spell’s light.
On each of your turns after you cast this spell, you can
use an action to move the beam 60 feet in any direction.