Hive Pack

The Hive Pack is an Expert Mode accessory found in the Treasure Bag dropped by the Queen Bee.

When equipped, friendly bees created by the caster -- whether summoned by the Bee Gun, Beenade, Honey Comb necklace or any other source -- have a chance to appear as a larger, more damaging version.

Trivia
Might be a reference to the video game The Binding Of Isaac:Rebirth's item Hive Mind, which increases the damage and size of friendly flies.