Swamp devils are formed under very special circumstances: a serial killer of strong will must be left to drown in a cursed swamp. This combination of evil magic and the serial killers own wickedness causes him to bond with the swamp. The transformation creates a swamp devil.
Swamp devils remember their past lives and seek to get revenge on those who left them to die. They are capable of moving about in human form within the limits of the swamp — usually several square miles. The swamp devil will use every trick at its disposal, including technology, to lure its victims to the swamp so it can enact its revenge.
Swamp devils are nearly impossible to destroy. They can be temporarily defeated by forcing them out of the boundaries of the swamp, but they merely reform. Ultimately, the best way to defeat a swamp devil may be to simply avoid it.
Swamp Devil (CR 4, HD 5d8+20)
NE Medium Plant (Aquatic)
Init +0 Spd 30 or Swim 20
Senses Low-light Vision (Ex); | Listen +3, Spot +3
AC 18 (FF 18, Touch 10)
hp 42 (Disabled -4/Dying -19/Injury 19)
Saves: Fort +8, Ref +1, Will +2
Damage Reduction (Su): 5/Bludgeoning, Immunity: Mind-Affecting Attacks (Ex), Immunity: Poison (Ex), Immunity: Sleep Effects (Ex), Immunity: Stun (Ex), Immunity: Polymorph (Ex), Immunity: Paralysis (Ex), Immunity: Critical hits (Ex)
Atk +7 base melee, +3 base ranged; Grapple +7;
+7 Melee (2 Slam 1d6+4/crit 20/x2);
+3 Ranged touch (6 Tendrils drag);
SA: Animate Vines (Sp)
SQ: Half Damage from Piercing (Ex), Half Damage from Slashing (Ex), Racial Traits: Plant, Malleability (Ex),
Abilities STR 18, DEX 10, CON 19, INT 9, WIS 13, CHA 10
Feats: Alertness, Blind-Fight.
Skills: Hide + 4, Listen + 3, Spot + 3, Swim + 16.
Animate Vines (Sp): A swamp devil can use this ability to animate any single vine or similar kind of plant life within 90 feet. An animated vine fights as an assassin vine in all respects (see the Monster Manual). An animated vine loses its ability to fight if the vine horror that animated it is incapacitated or moves out of range.
Malleability (Ex): Because of a swamp devil’s unusual body structure, it can compress its body enough to squeeze through a 1-inch-wide crack. Cracks and similar openings that are 1 inch or more in width do not slow the vine horror at all.
Plant Traits (Ex): A swamp devil is immune to poison, sleep, paralysis, stunning, and polymorphing. It is not subject to critical hits or mind-affecting effects. A vine horror also has low-light vision.
Tendrils (Ex): Most encounters with a swamp devil begin when it fires root-like tendrils. The creature can have up to two tendrils at once, and they can strike up to 50 feet away (no range increment). If a tendril is severed, the swamp devil can extrude a new one on its next turn as a free action.
Drag (Ex): If a swamp devil hits with a tendril attack, the tendril latches onto the opponent’s body. This deals no damage but drags the stuck opponent 10 feet closer each subsequent round (provoking no attack of opportunity) unless that creature breaks free, which requires a DC 23 Escape Artist check or a DC 19 Strength check. The check DCs are Strength-based, and the Escape Artist DC includes a +4 racial bonus. A swamp devil can draw in a creature within 10 feet of itself and bite with a +4 attack bonus in the same round. A tendril has 10 hit points and can be attacked by making a successful sunder attempt. However, attacking a swamp devil’s tendril does not provoke an attack of opportunity. If the tendril is currently attached to a target, the swamp devil takes a -4 penalty on its opposed attack roll to resist the sunder attempt. Severing a tendril deals no damage to a swamp devil.
Alternate Form (Su): A swamp devil can transform into its original humanoid form as a standard action. In its humanoid form it loses malleability, drag, and tendrils, but retains all other special abilities.
Rejuvenation (Su): In most cases, it’s difficult to destroy a swamp devil through simple combat: The “destroyed” spirit will often restore itself in 2d4 days. Even the most powerful spells are usually only temporary solutions. A swamp devil that would otherwise be destroyed returns to its old haunts with a successful level check (1d20 + swamp devil’s HD) against DC 16. As a rule, the only way to get rid of a swamp devil for sure is to determine the reason for its existence and set right whatever prevents it from resting in peace. The exact means varies with each devil and may require a good deal of research.
Swamp Dependent (Su): Each swamp devil is mystically bound to the swamp where it was created and must never stray beyond its border. If the swamp devil accidentally attempts to cross the border it loses one-third of its hit points with each attempt. If it is forced across the barrier against its will it is instantly destroyed.
For more info, see my review of Swamp Devil.