Shades of Darkness

I don't think so. At around the same time, Vitorrio managed to win on the test maps with a default build consisting of a Chaos character, a Dark Priest, and a Battle Mage. But subsequent enemies are not vulnerable to Chaos, so it's better to think in advance about switching to Darkness/Summoning on the Mentor before facing Yorgh. In my playthrough, Wisdom worked well – there's a guaranteed Tome of Power on the map, and with this combination, I was able to learn Shapeshift, Berserk, and Hive without the corresponding skill, which I used in the later stages.