Insanity. The derro has advantage on saving throws against being charmed or frightened.

Magic Resistance. The derro has advantage on saving throws against spells and other magical effects.

Sunlight Sensitivity. While in sunlight, the derro has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Spellcasting. Y is a 5th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 12, +4 to hit with spell attacks). The derro knows the following sorcerer spells:

Cantrips (at will): acid splash, mage hand, message, ray of frost

1st level (4 slots): burning hands, chromatic orb, sleep

2nd level (3 slots): invisibility, spider climb

3rd level (2 slots): blink, lightning bolt

Innate Spellcasting. Y can innately cast can cast the teleport spell once per day, but the intended destination must be within 30 feet of another society member. This teleport effect can be disrupted (see "Faerzress"), which is how society members sometimes end up in far corners of the Underdark, separated from their fellows.

Hooked Shortspear. Melee Weapon Attack: +2 to hit, reach 5 ft., one target. Hit:1 (1d4 - 1) piercing damage. If the target is a creature, the derro can choose to deal no damage and try to trip the target instead, in which case the target must succeed on a DC 9 Strength saving throw or fall prone.

Light Repeating Crossbow. Ranged Weapon Attack: +4 to hit, range 40/160 ft., one target. Hit:6 (1d8 + 2) piercing damage.