[Lazy_Perfectionist]

Disclaimer: I realize weapons already been created and my idea is too late. But I'll share it anyways.

Unique weapon for Agartha?
How about, 'Scepter of the Deep'?
Autocasts Darkness, grants Earthquake as a spell?
Obviously, you might need to tone it down.

Or casts Living Earth, or whatever that spell is that summons four/five earth elementals? Casting it for free (just 5 fatigue) on a unit tough enough to be placed on the front lines?