Looking through some of the Dark creatures, it got me on this train of thought when reading the surprisingly Lovecraftian mythos name of the Shaggoth-Zora.
So perhaps there are some forgotten and no longer worshiped Gods of Ancient Etheria that a few mages still follow. And since these forgotten ones largely exist between and in multiple dimensions, a follow must master arts of time-space, hence the Mage class title of "Rifter" or similar (Riftmaster, Riftlord, etc)
Even though it may be easy to place such a mage and his creatures/toolset in dark, I believe Arcane with a support of Dark would be the most thematic. Arcane creatures are full of the oddball and hard to pigeon hole type creatures, as well as the fact that in Lovecraft mythos, several lesser creatures and monsters are in fact simply aliens and/or results of experiments and dark engineering.
So, Rifter. Trained in Arcane and level 1 Dark. A mage feared for his ability to throw threats from any angle, and any time.
Channeling and other stats up for balancing, but likely geared toward something for just few creatures.
Abilities, potentially a self-targetable teleport quickspell. range of 1 zone away.
when casting creature spells, he may pay an extra mana tax (perhaps linked to level+) to place creature 1 zone away instead of own zone as default.
A mechanic similar to Druid's vine markers. But instead are rift markers. Up for discussion how similar or different they'll function to the vine markers.
Immune to a new status condition, "Unstable" that redirects forces and time. Similar to Daze, must roll to attack, if failed, then attacks highest level creature in zone if able, Mages included. Roll effect die to break ties.
Conjurations:
Possibly mostly incorporeal. A spawn-point that spits out creatures in a random 1 zone radius, roll to determine direction.
Another, a sort of 'alternate dimension' that locks those already in zone, unable to interact or be assisted by outside elements. A completely off limits zone for as long as the duration (dissipate style tokens) or until the conjuration is destroyed from inside the zone.
Portals. Pretty much similar to the hidden tunnels of Warlord, but must come in pairs or more. Allows mage and own certain type of creatures to teleport between.
Creatures:
Lots of tentacles, blobs, and other amorphous servants. Uncontainable being a common trait for the Rifter's roster. Perhaps some more tricky ones being mixed school, Arcane/Dark. The 'big' creature of his being able to move truly silently and mysteriously. The card possibly being kept out of the board, but in place is a small stack of tokens (perhaps just 2). These tokens move independently and simultaneously, following set rules and allowable move points. When ultimately conjoined again, they 'spawn' the creature for his action before resuming moving in the void again.
Enchantments:
Geared towards high mobility and placement, as well as instability of enemy actions. Perhaps one that makes a creature's move actions all considered teleport actions instead. And another that can make an enemy re-roll their attack (a reverse Akiro's Favor). A time slowing curse, which functions like a reverse defense, in what the target may roll a defense to avoid the coming but slowed attack.
Incantations:
Many will involve redirecting damage and flow of actions (time shifting). One could give a creature a trait similar to attacking conjurations, in that they read "Before or after any friendly creature activation, X may take X action" basically allowing two creature activations within a turn. (likely the casting cost+X of the creature for balance). Another that transports damage done to a target, such as attacking one creature, but the damage is instead inflicted on another legal creature elsewhere.
That's all I can come up with off the bat. I did try to stay away from some of the too Lovecraftian themes such as insanity and madnesses (that would be mind school anyways) but wanted to play the other angle that these creatures and any practitioners control space and a degree of time, as they can channel between dimensions and slip their will through various voids, keeping closer to established mage wars flavor rather than basically guest-staring the every-game's Cthulhu expansion.
