From Halopedia, the Halo wiki
Crafted in a similar shape to the Type-2 spike grenade, the dynamo grenade consists of a leather-wrapped handle with a squat metallic cylinder connected to the top. On this cylinder, three sharp fins protrude from its center. Yellow lights shine from the base of the handle and from around the cylinder structure.
When primed and thrown, the dynamo grenade emits electricity, even before contacting a surface. However, once it does come in contact with a surface, it begins arcing its electricity toward any targets within a certain radius. Much like the effects of the Banished's shock rifle, this electricity can arc from the nearest target to any other nearby target, dealing damage to all that are unfortunate enough to be so tightly gathered. The dynamo grenade also appears to be able to arc its electricity off of most metallic objects, whether intended targets or not. Some vehicles like the M12B Warthog and Banished Ghost can become temporarily disabled if caught within the grenade's radius. After thrown, the grenade only lasts a few seconds before ultimately detonating, all the while emitting a beeping sound at an increasing rate until detonation.
The dynamo grenade is usable in Halo Infinite's multiplayer. With default settings, players can hold two dynamo grenades. When thrown, the grenade's electricity will arc toward nearby enemies, vehicles, dropped weapons, and other metallic gameplay objects. Like the shock rifle, this electricity can then arc toward other viable enemies or items within a certain radius. However, the electricity will not arc toward the bodies of dead players. If a drivable vehicle gets caught within the radius of an active dynamo grenade, it will become temporarily disabled. After thrown, the grenade will only rest on the ground for a few seconds before detonating.
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