Calls forth a creature that is antithesis to Creation that tears at reality. It can be controlled to some degree and directed, at least initially, but as it enters a mutual annihalation with the created world, anything could happen.
DEEEEEEEEP CROOOOOOOOOOOOOW
Cast once, limited time effect.
Perverts and corrupts the natural fabric of the world to distort a natural force such as the waves of the sea or a rain cloud. As this happens, he usual effect of the natural force becomes extremely corrupt (acid raid, tsunamis etc).
Cast once, single/persistent effect?
Summons forth from the dimensions Beyond a plague of swarming horrors which blight the lands and torment the people. They are undirectable and will do widespread damage, causing unpredictable chaos. Different from TBotST because they spread wider, do more damage (which is much more thinly spread), and cannot be pointed at something - like, say, a city. See also: Rev. 9, 1-11
Cast once, limited time effect.
Reveals metaphysics and/or other information, like divination only far more hardcore and useful. Often drives user irreparably mad.
Cast once, technically single effect (though the knowledge stays with you).
You conjure unearthly riches by channelling the creative power of those Beyond. These riches are enticing and are enough to tempt the most pious and ascetic of hearts. However, they are ephemeral and not of this world; they are likely to fade and they're not quite… right - almost too fantastic.
Cast multiple times, limited time effects.
Form 1: Can copy any spell from any of the non-Divine/non-Ancient spell lists, up to Tier 3. It costs 1 less AP to cast these spells (down to a min. of 1), at the cost that this usually perverts the spell in some way, and the effects are often short and unpredictable.
Form 2: Gives you all the T4 Ancient variant spells, though less perverted.
Cast once, always on (adds other spells to your spell list).
Transforms the caster into a horrific monstrosity, channelling Ancient power directly through their body. As the power of the Others courses through their veins, they begin to unleash destruction upon the world. Their flame burns a bright blinding black and consumes them utterly as they wreak wrack and ruin upon the world.
Kills the caster (obviously).
Cast once, single effect. Just you try to cast this one twice…