The sensation of that process could be described as searing cold or burning light, depending on how the metaphysics of it would be portrayed.
For weaker Spirits, this could cause visible fragmentation, resulting in parts of their form flickering, smoking, or dissolving due to their being unable to cross without severe harm.
If they tried to escape them forcefully, it could cause permanent damage to their essence that could be difficult to recover from, while there would be a possibility that they could end up dispersing entirely.
Stronger Spirits could force their way through, but it would still come with a cost.
The ash would still tear at their Life Energy in ways that could leave them weakened, unstable, or scarred.
