Gronco (The Thing) is a colossal SoulDreg classified as a Void Irregulus. It was originally sealed into District 6 by Ladi but Lakasha's intervention with the player causes the seal to break and allows Gronco to resurface. It currently cannot be killed and retreats into the Void after its defeat. It serves a world boss.
Gronco's story changes with the world boss revamp.
The SFL was able to determine that Gronco would revived based on the recent energy readings in area. The player was able to defeat Gronco and had a strange feeling that they were not fighting alone. Shiho explains that due to the constant twisting of the dimensions, all of the souls from the parallel unified together to support the cause but were not together in the same physical world.
The Castle Wall series barricade used in the Starry Shield operation where also deployed against Gronco in Ladi's fight.