Acid Shells is a Sobek-exclusive mod that causes enemies killed by the Sobek to explode, dealing a flat amount of Corrosive damage plus a percentage of the enemy's maximum health as Blast damage in an area of effect.
Due to the nature of this mod, prioritizing heavy units will result in other enemies taking high damage or dying due to the resulting explosion, reducing the time to kill entire crowds significantly.
Modding the Sobek for Corrosive or Viral damage and punch through can be effective to soften up enemies at higher levels with procs before the explosion occurs, thus amplifying the damage inflicted by Acid Shells' burst.
Against the Infested, this mod scales tremendously well since most of them have no armor.
This mod, along with the other Executioner mods, are the second set mods to feature non-generic enemies on the mod card, the first being Vengeful Revenant.
At the time of Operation: Rathuum's announcement, this mod was referred to as Execution Shells, likely an earlier name for the mod. This initially caused confusion with players trying to look for the nonexistent mod.