The greatest negative effect of turning into an Evil Spirit would be the serious harm to one's intelligence.
Nothing could be done about that.
Many Evil Spirit Envoys were troubled about it. If they wanted to become big shots of the Negative Energy Plane, then they needed a way to withstand the negative energy invading their minds.
Dragon God Hartson, Diggles, and the like, naturally had their own methods.
But ordinary Evil Spirits didn't enjoy such advantages.
Like the two Dragons who became corrupted.
This was considered the biggest disadvantage of Evil Spirits. There was no lack of intelligence for the powerhouses, but their subordinates were somewhat retarded...
The Evil Spirit Sea gave them formidable power, but the power of negative energies came with a price. After their intelligence was impaired, they could only follow orders and lost the most basic ability to make proper judgements.
