I love Roiling Incant! The creature itself is dangerous ongoing spell energy gone berserk, a mindless, magical force of energy that’ll destroy anything it encounters. They make great wandering monsters in magic-laden areas, backlashes for critical failing a ritual or even hazard-like puzzles! Each is keyed to a specific Tradition and School. The base Roiling Incant from Bestiary 3 uses Arcane and Evocation, but any school and tradition are theoretically possible!
Before we begin, I want to note that different flavors of Evocation are going to be the quickest and most obvious Roiling Incant you can design. Pick some solid damage spells, maybe some area of denial, and you’re good to go! But I believe there’s room for every school of magic with this wonderful creature, and I’d love to see what we can get when we try! So, please, feel free to make your own and post them!
Arcane Abjuration (Bubbles!)
The abjuration roiling incant resembling a sphere of force the most defenses of any other, able to spam shield and shattering gem to at least try to offset its loss of hit points as it uses unstable magic. It can try to catch enemies in the resilient sphere, but its primary tactic is to destroy magic. This enemy is best used when there is a sensitive ongoing spell effect or ongoing ritual that would be heavily disrupted by dispel magic, and keeping the roil from the ritual should be the player’s primary focus while this roil is causing chaos. Alternatively, you could set the monster in a room that begins to fall apart when hit by dispel magic, such as a valley flooded with “resilient spheres” produced by the ritual that spawned the roil, capable of quickly becoming “pits” as the roil begins to spam selective dispel magics (which requires some GM fiat, but it makes for a fun encounter).
Arcane Conjuration (Coral!)
This conjuration roiling incant is themed all about water and looks like a ball of coral. It has the aquatic trait and a swim speed. It can slow enemies down with a mud-pit and even dash them away with an aqueous orb, setting up the battlefield for painful coral eruptions. I love the idea of this as the result of an arcane ritual that was attempting to extract power from a ravaged coastline or coral reef.
This ball of eyeballs is the most reliant on their melee strikes, as it wants to spam true strike. It can also throw ill omen on a creature who might actually pose a threat. It seems dead-set on heading in a single cardinal direction, even if that means destroying structures that lay between it and its unknown situation!
Occult Enchantment (Fear!)
This sphere of uttermost fear looks to each creature like a warped lens into their own nightmares. It runs around sewing confusion and chaos as it spreads fear across the land, probably attracting a will-o-wisp or two whose anti-magic properties would leave it practically invisible to the rampaging roil.
Occult Illusion (Ritualists!)
This shimmering banner of colors is always accompanied by a number of mysterious robed spellcasters, chanting in some familiar and yet completely indiscernible tongue. A wonderful manifestation of a ritual gone awry, this incant can replicate the ritualists to protect itself as it slowly roils across the countryside, perhaps looking to use its cacophonic sounds to recreate the potentially destructive ritual that gave it life!
Divine Necromancy (Blood!)
This roiling blood sphere makes a great set-piece for a failed attempt to rid a dhampir of its vampiric heritage, or even become a vampire without one’s assistance. The roiling sphere can suck up blood, although if you want to remove its healing restriction and let it slurp back up that blood to reform that would make it a considerably more challenging threat!
Primal Transmutation (Clay!)
And last, but certainly not least, we have our transmutation roiling incant! I feel like this ball of clay has the potential for the most heart-wrenching backstory, given its cantrip probably infers that it was originally a failed attempt at healing, whether it was a person or an entire field of dying crops! It also has the most potential for collateral damage, rolling around towns or farms completely reshaping the landscape as it goes, potentially leaving crude statues of the creatures it was unable to save!