Tathrug the Shellwise

Multiattack. Tathrug makes two attacks: one Staff Strike and one Bite, or it may make two Staff Strikes.

Staff Strike. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 18 (2d10+7) bludgeoning damage plus 7 (2d6) radiant damage.

Bite. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 15 (2d8+6) piercing damage. If the target is a creature, it must succeed on a DC 18 Strength saving throw or be knocked prone as the shell's momentum topples it.

Adamentine Shell. Tathrug withdraws into its shell as an action. Until it emerges (bonus action), it gains +4 AC, resistance to all damage except force and radiant, and any creature that starts its turn within 10 feet of Tathrug must succeed on a DC 18 Wisdom saving throw or be stunned until the start of its next turn as the weight of ages presses on its mind. Tathrug can end shell form early as a bonus action.

Moment of Stillness (Recharge 5-6). Tathrug raises its staff and exhales a sound like an old bell. Each creature of Tathrug's choice within 60 feet that can hear it must make a DC 18 Wisdom saving throw. On a failed save, a creature takes 45 (10d8) psychic damage and is paralyzed for 1 minute. On a successful save, the creature takes half as much damage and is not paralyzed. A paralyzed creature can repeat the save at the end of each of its turns, ending the effect on a success.

Ancient Counsel (1/Day). Tathrug touches a willing creature and bestows a vision of ages. The target gains truesight to 60 feet and a +5 bonus to Wisdom and Intelligence checks for 1 hour, but the recipient ages 1d10 years mentally (no mechanical age effects unless the DM decides).

Shell Retort. When a creature hits Tathrug with a melee attack, Tathrug can use its reaction to force the attacker to succeed on a DC 18 Strength saving throw or be pushed 15 feet away and fall prone.

Detect. Tathrug makes a Wisdom (Perception) check.

Slow Step. Tathrug moves up to half its speed without provoking opportunity attacks.

Quiet Tap (Costs 2 Actions). Tathrug strikes the ground with its staff; one creature within 10 feet must succeed on a DC 18 Constitution saving throw or have its speed halved and its action used only for the Dash, Disengage, or Dodge action until the end of its next turn.