Compatibility, the measure which served as a means to determine the harmony between concepts.
It was a major aspect of the supernatural, one that utilized the concept of balance that reigned over Eventide to determine the relationship between concepts.
Just as how water served as a counterbalance for fire and how wind served as a counter for lightning.
Of course, it wasn't completely straightforward when one got into tricky fields like Psionics or even Spiritomancy but that didn't mean it didn't work the same.
One's understanding of Compatibility was imperative when facing off against opponents as unfavorable compatibility would result in them being defeated even if they were to be at a higher level mystically.
It was just how it was in the esoteric world of mysticism.
It wasn't just about how many Locks one had unlocked or how many Abilities one had.