Beenade

Same fuse and same bounce as a plain grenade, but the blast is only the opening. A cloud of bees pours out and goes hunting on its own, so the throw does not have to be accurate. Land it near the target and the swarm sorts out the rest.

Open ground. Each bee is limited by how many times it can pierce or ricochet, and a tight tunnel burns those on walls before the bees ever reach anything. In a wide arena they spend every one of them on the target instead, which is a large difference in total damage from the same throw.

A bee that touches water or lava is gone on contact, and one of these detonating in either liquid produces no swarm at all. Honey is survivable but the bees crawl through it. That writes the weapon off for most of the Underworld and a good part of the Jungle, which is unfortunate given where you get them.

The explosion counts as a normal ranged hit and picks up your critical chance and effects like the frostbite from Frost armor. The bees do not. They take flat ranged damage bonuses and nothing else, and they can never land a critical hit, so stacking critical chance for the swarm is wasted. A Hive Pack is the upgrade that genuinely changes them, converting a good share of the swarm into the larger, faster, longer lived version.