You summon 1d4 Nightwing Bats from the pits of hell to fight along side you for 1d4 rounds.

Each beast is  disappears when it drops to 0 hit points.

The summoned creatures are friendly to you but not your companions and will attack them and any other creature in the vicinity. Roll initiative for the summoned creatures as a group, which has its own turns. They obey verbal commands in Infernal from the caster if told not to attack specific people. 

The GM has the creatures' statistics.

Nightwing Bat

Armor Class 13

Hit Points: 13 (1d12 + 2) 

Speed: 20 ft., fly 90 ft.

Challenge 0 (10 XP)

ACTIONS

Multiattack. The bat makes two attacks: one with its bite and one with its claws.

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 8 (1d10 + 3) piercing damage.

Claw. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 7 (1d8 + 3) slashing damage

At Higher Levels. When you cast this spell using certain higher-level spell slots, you choose one of the summoning options above, and more creatures appear: twice as many with a 5th-level slot, three times as many with a 7th-level slot, and four times as many with a 9th-level