ooc: Ah... natural true sight, good of you to mention that...
Isul's spell registered a moderately powerful aura on Drannoth.
[If you make Spellcraft DC20]
The aura was a transmutation effect of Supernatural nature.
Isul's spell registered a second dim residual aura.
[If you make Spellcraft DC35]
The aura was undoubtedly a Transmutation effect of considerable power, again of Supernatural nature, but it's workings had stopped, it was no longer active.
In True Sight, Drannoth looked double-formed: The tentacled mass was super-imposed on his normal Drow form, as was common for subjects of shape-changing magic.