From Destinypedia, the Destiny wiki
Acolyte Grenades are a type of Solar magic explosive conjured and fired by Hive Acolytes in Destiny 2. They were later adopted and used by Dul Arath, Retainer of Xivu Arath, and several other Ultra Knights.
As opposed to the Shock Grenades used by Fallen Dregs, Acolyte Grenades explode instantly upon impact with the ground, leaving behind a pool of fire which causes damage overtime. This requires players to be wary of when they are thrown, since they won't have a chance to escape from damage once the grenades have landed, along with dealing noticeable contact damage. Acolytes tend to use them as a tactic to force enemies out into the open from their cover or if they're staying too far away to be attacked with Shredders.
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