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As for Essence not all abilities use Essence in Classic Unisystem from what I have seen. Psychic Powers do not, if I recall correctly. Only Magic and Miracles, if I recall.


Psychic (Seer) Powers do not require essence, though they can be boosted with it. They cost about 2.5x more than Invocations do, however. this cost is due to invocations requireing large essence pools to fuel them and essence channeling to draw out the essence.
All other metaphysics use essence (Chi powers, Miracles, Necromancy, Primal powers, Spirit powers, Theopanies, Tao-chi. . . .) except for the ones that use taint instead.
though some (such as necromancy) can make do without essence chanelling and just use rituals instead.

Consequently when you translate a power into classic you would generally add it to the vast majority of powers fueled directly with essence.