Echolocation. The hook horror can't use its blindsight while deafened.
Keen Hearing. The hook horror has advantage on Wisdom (Perception) checks that rely on hearing.
Multiattack. The hook horror makes two hook attacks.
Hook. Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit: 11 (2d6 + 4) piercing damage.