Tesso 鉄鼠

Large fiend (demon), chaotic evil

Armor Class 17 (natural armor)

Hit Points 127 (15d10 + 45)

Speed 40 ft., climb 30 ft.

STR 18 (+4) · DEX 16 (+3) · CON 16 (+3) · INT 13 (+1) · WIS 14 (+2) · CHA 18 (+4)

Saving Throws Str +7, Cha +7

Skills Athletics +7, Intimidation +7, Perception +5, Stealth +6

Damage Resistances cold, fire, lightning; bludgeoning, piercing, and slashing from nonmagical attacks

Damage Immunities poison

Condition Immunities poisoned

Senses darkvision 60 ft., passive Perception 15

Languages Abyssal, Common, Yokai Speech

Challenge 7

Traits

Iron Hide. Tesso has resistance to bludgeoning, piercing, and slashing damage from all sources unless the attack is made with a magic weapon. (If you prefer standard fiendish resistance, remove this trait.)

Rat Mastery. Rats and rat swarms are naturally inclined to obey Tesso. As a bonus action, Tesso can issue a simple command (move, guard, attack, etc.) to any rat swarm or giant rat within 60 feet that can see and hear it. The commanded rats act on Tesso’s turn.

Magic Resistance. Tesso has advantage on saving throws against spells and other magical effects.

Actions

Multiattack. Tesso makes two Claw attacks or one Claw attack and uses Bite.

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target.

Hit: 13 (2d6 + 4) slashing damage. If the target is a creature, it must succeed on a DC 14 Constitution saving throw or become cursed until the end of its next turn. While cursed in this way, the target’s speed is reduced by 10 feet, and it can’t take the Dash action.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target.

Hit: 14 (2d8 + 4) piercing damage plus 7 (2d6) necrotic damage. If the target is a creature, it must succeed on a DC 15 Constitution saving throw or become diseased. While diseased in this way, the target has disadvantage on Strength and Dexterity saving throws. The target can repeat the save at the end of each long rest, ending the effect on itself on a success.

Summon Rat Swarm (Recharge 5 - 6). Tesso calls forth a writhing mass of rats. A swarm of rats (MM p. 339) appears in an unoccupied space within 30 feet of Tesso, acts on Tesso’s initiative (immediately after Tesso), and obeys its telepathic commands. The swarm remains for 1 hour, until Tesso dismisses it (no action required), or until Tesso drops to 0 hit points.

Devour Manuscript (1/Day). Tesso targets a nonmagical book, scroll, or similar written text within 5 feet and devours it with supernatural speed. Any knowledge or secrets therein are lost forever (unless recovered by a powerful greater restoration or wish spell at the GM’s discretion). If the written item is magical, Tesso must succeed on a DC 16 Constitution saving throw or take 10 (3d6) force damage and fail to devour it.

Reactions

Vengeful Lash. When a creature within 5 feet of Tesso misses Tesso with a melee attack, Tesso can make one Claw attack against that creature.

Lore

Rat-like monk spirit clad in iron, born from obsessive rage against priests.

The legend of Tesso (literally “Iron Rat”) connects to a real historical figure: the Buddhist monk Raigo Ajari. His story is documented in Buddhist chronicles, which tell of Emperor Shirakawa, fervently longing for an heir. Hoping for divine favor, the emperor requested the head priest of Mii-dera to have his monk, Raigo, pray day and night for the birth of a son. Renowned for his piety and spiritual power, Raigo took it upon himself, with utmost devotion, to help the emperor. When Emperor Shirakawa asked Raigo what reward he desired if the prayers were successful, the monk asked that Mii-dera be allowed to take on fifty new novices, thereby expanding the temple.

After many nights of prayer, Fujiwara no Kenshi conceived, and Prince Taruhito was born. However, when it came time to grant the promised reward, complications arose. Rival monks from Enryaku-ji pressured the emperor to renege - their motives uncertain, though likely driven in jealousy and unwillingness to let Mii-dera become the dominant temple of Shiga Prefecture. Feeling betrayed and enraged, Raigo declared a hunger strike to protest the ruler’s injustice. In the end, he died, cursing the emperor and his bloodline. Rumor has it that, in his final days, Raigo lost his grip on sanity, casting dark curses on all his adversaries in the neighboring temple and praying to demons.

From Yokai Bestiary 5E, p. 10 · Fern Flower Press