IDEA: "Spectral" abilities.

[Zero the Dragon King]

Basically, spectral abilities would be "elemental" passives that benefit varied parties, as opposed to parties consisting of only one affinity.

Spectral Invocation: Boost the damage for all party members of different affinities. (Boosts the entire party only if all members are of different affinities.)

Spectral Ward: Protect all party members from those of their opposing affinities. (Terra > Spirit + Lunar, Spirit > Terra + Abyss, Primal > Lunar + Abyss, Lunar > Terra + Primal, Abyss > Spirit + Primal)