According to the map, your party had another day of travel before reaching a bridge crossing the rain-swelled river baring your progress. As luck would have it, though, an abandoned trade road you ran across still has an intact bridge spanning the turbulent water. The bridge wasn't on the map, but such oversights are not uncommon. What wasn't common was your boots sticking to the stones halfway across. Railing transformed into tendrils. and the bridge just twisted itself to throw the wizard into the rushing river below. It's yet another damn mimic... roll for initiative

The bridge mimic's origin is simple enough. The breed is attracted to bodies of water and finds troll flesh downright addictive. To take on a troll, well, first one has to use acid to stop them from regenerating and mimics can do that. Second, you have to be big enough and tough enough to weather their attacks. Third, as a mimic anyway, you have to take a form they find attractive. Thus, a bridge! Plus, all sorts of travelers and animals naturally use bridges to cross rivers and other spans, so why not? One unexpected benefit comes from eating trolls as well, the mimic mimics their regeneration with a small difference.

Bridge Mimic

Huge Mimic (shapechanger), neutral

Armor Class 16 (natural armor)

94 (9d12 + 36)

Speed 15 ft

Str 24 Dex 6 Con 18 Int 5 Wis 16 Cha 10

Skills Stealth +4

Damage Immunities acid

Condition Immunities prone

Sensesdarkvision 60 ft, passive Perception 13

Languages -

Challenge 6 (2,300 XP)

Shapechanger.

The mimic can use its action to polymorph into a bridge or back into its true, amorphous form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Adhesive (Object Form Only).

The mimic adheres to anything that touches it. A Huge or smaller creature adhered to the mimic is also grappled by it (escape DC 18). Ability checks made to escape this grapple have disadvantage. The mimic can turn on and off this ability as a bonus action.

False Appearance (Object Form Only).

While the mimic remains motionless, it is indistinguishable from an ordinary bridge.

Grappler.

The mimic mimic has advantage on attack rolls against any creature grappled by it.

Nridge Toll.

The mimic regains 10 hit points at the start of its turn. If the mimic takes fire or thunder damage, this trait doesn't function at the start of the mimic's next turn. The mimic dies only if it starts its turn with 0 hit points and doesn't regenerate.

Actions

Multiattack.

The mimic makes two pseudopod attacks and one bite attack.

Pseudopod.

Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 11 (1d8 + 7) bludgeoning damage. If the mimic is in object form, the target is subjected to its Adhesive trait.

Bite.

Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 13 (1d10 + 7) piercing damage plus 9 (2d8) acid damage.

Troubled Waters (Recharge 5-6).

The mimic targets a body of water it can see within 120ft that is also at least 30 feet square and 10 feet deep. It causes a whirlpool to form in the center of the area. The whirlpool forms a vortex that is 5 feet wide at the base, up to 30 feet wide at the top, and 10 feet tall. Any creature or object in the water and within 25 feet of the vortex is pulled 10 feet toward it. A creature can swim away from the vortex by making a DC 14 Strength (Athletics). When a creature enters the vortex for the first time on a turn or starts its turn there, it must make a DC 14 Strength saving throw. On a failed save, the creature takes 9 (2d8) bludgeoning damage and is caught in the vortex until the spell ends. On a successful save, the creature takes half damage, and isn't caught in the vortex. A creature caught in the vortex can use its action to try to swim away from the vortex as described above, but has disadvantage on the Strength (Athletics) check to do so. The first time each turn that an object enters the vortex, the object takes 9 (2d8) bludgeoning damage, this damage occurs each round it remains in the vortex. This vortex lasts 1 minute and ends early if the mimic is incapacitated or slain.