Name: Cù Sìth
Large fey, chaotic neutral
Armor Class 16 (natural armor)
Hit Points 150 (12d10 + 84)
Speed 50 ft.

STR 23 (+6)
DEX 18 (+4)
CON 24 (+7)
INT 10 (+0)
WIS 16 (+3)
CHA 14 (+2)

Skills Perception +7, Stealth +8
Damage Immunities poison
Condition Immunities poisoned
Senses darkvision 120 ft., passive Perception 17
Languages understands Common and Sylvan but can't speak
Challenge 11 (7,200 XP)

        Keen Hearing and Smell. The Cù Sìth has advantage on Wisdom (Perception) checks that rely on hearing or smell.
        Magic Resistance. The Cù Sìth has advantage on saving throws against spells and other magical effects.

Actions
        Multiattack. The Cù Sìth makes two bite attacks.
        Bite. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 24 (4d8 + 6) piercing damage.
        Claws. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 18 (3d8 + 6) slashing damage.
        Frightful Presence. Each creature of the Cù Sìth's choice within 30 feet of it and aware of it must succeed on a DC 15 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the Cù Sìth's Frightful Presence for the next 24 hours.

Legendary Actions
        The Cù Sìth can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Cù Sìth regains spent legendary actions at the start of its turn.
        Move. The Cù Sìth moves up to its speed without provoking opportunity attacks.
        Bite (Costs 2 Actions). The Cù Sìth makes one bite attack.
        Foretell the Future (Costs 3 Actions). The Cù Sìth chooses a target within 60 feet and predicts a future event related to that target. The target must succeed on a DC 18 Wisdom saving throw or be cursed with a prophetic vision that will come true within the next 24 hours. The Cù Sìth cannot use this ability again until it completes a long rest.

Description: The Cù Sìth is a mythical creature from Scottish folklore that is said to resemble a large, fearsome hound. According to legend, this creature is roughly the size of a young bull, with shaggy fur that is typically dark green or black in color. Its eyes are said to glow with a fiery intensity, making it a particularly fearsome sight to behold.

In some versions of the legend, the Cù Sìth has a long, curling tail and sharp, pointed teeth that are capable of tearing through even the toughest of hides. It is also said to have razor-sharp claws, which it uses to dig through the earth and to rip apart its prey.

Despite its terrifying appearance, however, the Cù Sìth is believed to have a somewhat supernatural quality to it. In some stories, it is said to have the power to transform itself into a human, and is said to be particularly fond of music and dancing. In others, it is said to be capable of foretelling the future or even of granting wishes to those who are brave enough to approach it.

Overall, the Cù Sìth is a fascinating and complex creature that has captured the imaginations of generations of Scottish storytellers and folklorists. Whether seen as a fearsome guardian of the wilds or a mysterious and magical creature, it remains an important part of Scotland's rich cultural heritage.