A few spells were added to various classes as drops from specific raid bosses in very late Velious. (Nov 2001) This is what I've found so far:
Dementing Visions:
https://web.archive.org/web/20011123...info/2016.html
Dropped from Aaryonar and King Tormax
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Conglaciation of Bone:
https://web.archive.org/web/20011121...ll/update.html
This one seemed to have shown up alongside some Luclin spells in this spells list in Nov 2001, which was probably ripping them from a newly updated spells-us.txt preparing for Luclin? Although both Conglaciation of Bone and Dementing Visions show up lower down on the list before most of the Luclin spells, alongside spells that currently do exist on P99 like Incinerate Bone.
Dropped from Derakor the Vindicator, Jorlleag and a few trash spiders in velks