MM page 279
Incorporeal Movement. The specter can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) 1d10 force damage if it ends its turn inside an object. Sunlight Sensitivity. While in sunlight, the specter has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.
Life Drain. Melee Spell Attack: +4 to hit, reach 5 ft., one creature. Hit: (3d6) 3d6 necrotic damage. The target must succeed on a DC 10 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the creature finishes a long rest. The target dies if this effect reduces its hit point maximum to 0
Dwellers in Darkness. Sunlight represents a source of life that no specter can ever hope to douse, and it pains them. When night falls, they leave their final resting places in search of living creatures to slay, knowing that few weapons can harm them in return. At the first light of dawn, they retreat back into the darkness, where they remain until night falls again.