Lesser Shadowfallen (5e Template)
From D&D Wiki
A shadowfallen creature, or "Shadow", is the bleak echo of its soul's innate evil; it either materializes in the Shadowfell from corruption by the plane of shadow, or is manifested via ritual of dark necromancy. A creature with a prominent soul, used to form a shadow, may have lightly-glowing pupils for eyes like toasted cinders in a fire pit, or deeper, darker holes where eye sockets would be, which seem to absorb all light near them.
Must be an Aberration, Beast, Celestial, Dragon, Elemental, Fey, Giant, Humanoid, Monstrosity, or a Plant with intelligence above 2.
Hit Dice. Its hit die decreases by one stage (d10 > d8), to a minimum stage of d6.
Damage Immunities. Necrotic
Damage Resistances. (In Darkness) Acid, Cold, Fire, Lightning, Thunder; Bludgeoning, Piercing, and Slashing from nonmagical attacks
Damage Vulnerability. Radiant
Condition Immunities. Exhaustion, Frightened.
Skills. It gains proficiency in Stealth, Its proficiency bonus is doubled for Stealth checks.
Darkvision. The creature gains darkvision to 60 feet. If it already had it, it gains another 30 feet.
Living Shadow. While in darkness, the creature has resistance to damage that isn't force, psychic, or radiant.
Shadow Stealth. While in darkness, the creature can take the Hide action as a bonus action and gains a bonus equal to its proficiency on such attempts to sneak.
Sunlight Weakness. While in sunlight, the creature has disadvantage on attack rolls and saving throws, as well as on Wisdom (Perception) checks that rely on sight.
New Action: Strength Drain. Using the primary melee attack of the former creature (and its bonuses to attack and damage rolls), the creature deals necrotic damage, and the target's Strength score is reduced by 1d4. The target dies if this reduces its Strength to 0. Otherwise, the reduction lasts until the target finishes a short or long rest. If a humanoid dies from this attack, a new shadow rises from the corpse 1d4 hours later. The shadow is under the creature's control.
New Action: Shadow Breath. If the former creature has an innate natural ranged attack such as a breath weapon, the attack deals necrotic damage instead of its original damage type. A creature reduced to 0 hit points by this damage dies, and an undead wraith rises from its corpse and acts immediately after the creature's in the initiative count. The wraith is under the creature's control.