Sources
CR
Type
Size
Alignment
Movement

Gibberling

Small Aberration, Chaotic Neutral

Armor Class 12
Hit Points 7 (2d6)
Speed 25 ft., burrow 5 ft.
STR
10
+0
DEX
15
+2
CON
10
+0
INT
6
-2
WIS
8
-1
CHA
8
-1
Skills Stealth +4
Damage Resistances psychic
Condition Immunities Charmed, Frightened
Senses darkvision 60 ft., passive Perception 9
Languages
Challenge 1/4 (50 XP)

Traits

Light Sensitivity. While in bright light, gibberlings have disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Reckless. At the start of its turn, the gibberling can gain advantage on all melee weapon attack rolls during that turn, but attack rolls against it have advantage until the start of its next turn.

Actions

Dagger. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit:4 (1d4 + 2) piercing damage.

Swarm. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. If the target is a Medium or smaller creature, it has the grappled condition (escape DC 10). All gibberlings within 5 feet of the target can use a reaction to make a Dagger attack with advantage on the attack roll.

Burrow. The gibberling burrows into the dirt, giving itself the prone condition. It has advantage on Dexterity (Stealth) checks while it is prone.

Lore

Gibberlings are appropriately named, for they babble, or should I say gibber, incessantly. They are unpredictable and thus barely worthy of any kind of research. Thus, why I didn't include them in my book "Volo's Guide to Monsters".