Sources
CR
Type
Size
Alignment
Movement

Skum

Medium Aberration, Lawful Evil

Armor Class 14 (natural armor)
Hit Points 93 (11d8 + 44)
Speed 20 ft., swim 40 ft.
STR
19
+4
DEX
11
+0
CON
18
+4
INT
7
-2
WIS
12
+1
CHA
9
-1
Skills Perception +4
Damage Resistances psychic
Senses darkvision 120 ft., passive Perception 14
Languages Common, Deep Speech, telepathy 60 ft.
Challenge 5 (1,800 XP)

Traits

Abolethic Vassal. The skum is permanently charmed by its aboleth master.

Amphibious. The skum can breathe air and water.

Psychic Conditioning. The skum is immune to the frightened and charmed conditions unless they are from effects created by an aboleth.

Water Dependency. The skum takes 6 (1d12) acid damage every 10 minutes it goes without exposure to water.

Actions

Multiattack. The skum makes three attacks: two with its trident and one with its Mind-Breaking Touch.

Trident. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:7 (1d6 + 4) piercing damage.

Mind-Breaking Touch. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:18 (4d8) psychic damage, and the target has disadvantage on Wisdom saving throws until the end of the skum's next turn.

Lore

Several poor souls around the Styes have succumbed to an aboleth's magic through its disease-bearing touch. Transformed into creatures called skum, they barely resemble their past forms, their skin turning slimy and translucent while their limbs warp to resemble those of deep-sea oddities. The change makes them dependent on water, which they must immerse themselves in regularly lest they experience painful-and potentially lethal-skin eruptions. Skum are bound to their aboleth master not just by…