what does a hollow soul do in vv ultimatum

A Hollow Soul in VV Ultimatum is an item/material used for crafting, and the public item listings say it is crafted from 3 Hogyoku Shards, 4 Dark Essence, and 1 Soul Chain. Its exact use is still listed as currently unknown in the material database.

What that means

• It is not described as a combat skill or form by the source I found.
• It appears to be a crafting-related item rather than something you actively “use” for a direct ability.
• Community guides around Hollow progression focus more on Menos, Adjuchas, Vasto Lorde, Arrancar, and Resurrection, not on Hollow Soul as a progression step.

In plain terms

If you got a Hollow Soul, the safe answer is: hold onto it as a crafting material until the game or a later guide confirms its exact recipe use. The item databases currently label it as unknown, so any more specific claim would be guesswork.

TL;DR

Hollow Soul is a crafting material in VV Ultimatum, but its final use is not yet clearly documented in the sources I found.