u/Funtomcoop

If a random encounter ensues in total darkness in a place where the Shadowdark is ever-present, roll another 1d6. On anything beside a 1, roll on the random encounter table. On a 1, the party encounters a grue.

Grue
It is pitch black. You are likely to be eaten by a grue.
AC 14, HP 22, ATK 2 claw +4 (1d6) or 1 bite +3 (1d8+swallow), MV near, S +4, D +4, C 0, I -3, W +1, Ch -1, AL N, LV 5
Swallow. DC 14 STR or swallowed whole. Total darkness inside and 1d10 damage per round. Grue regurgitates if dealt at least 10 damage in one round to the inside of its gullet.
Light sensitivity. Grue takes 1d4 damage per round while light shines on it. It also has disadvantage on tasks that require sight.