Summoning is used by a character to exert change upon their surroundings by manifesting creatures from elsewhere or 'out of thin air'. Further, a character usually has control over the things they've summoned.
Effect: Summoning is usually used on actions to add a Asset to the Scene that simulates a summoned 'creature' of some sort that is under the summoner's control. The Asset can be added to subsequent dice pools to represent the summoned 'creature' lending its aid to the summoner or their allies as relevant. These 'creatures' can also be used to provide narrative justification; for instance a summoned steed can greatly aid rapid travel.
At d4 Summoning manifests as a minor non-threatening nuisance such as a bug or a rabbit or a lap dog.
At d6 Summoning manifests as a useful minion or a creditable threat such as a pony or a guard dog or a minor imp, or a pack of d4 minions.
At d8 Summoning manifests as a very useful minion such as a warhorse or a bear or an imp, or a pack of d6 minions, or a bunch of d4 minions.
At d10 Summoning manifests as an extremely useful minion such as a griffin or unicorn or a demon, or a pack of d8 minions, or a bunch of d6 minions, or a swarm of d4 minions.
At d12 Summoning manifests as a supremely useful minion such as a dragon or giant or demon lord, or a pack of d10 minions, or a bunch of d8 minions, or a mob of d6 minions, or a horde of d4 minions.
Common SFX: The Constructs SFX can be taken to improve a character's summoning capabilities.
The Telesensory SFX can be taken to allow a character to share sensory information with one or more of their summoned minions.
Common Limits: Summoning is often paired with the Spell Components Limit to represent the necessity for mystic passes, incantations, and / or material components, but this is not required.
Summoning is often paired with a Limit that narrows what kinds of things can be summoned; for instance Animal Summoning vs Demon Summoning, but this isn't required.
A character might take the Free Agent Limit to indicate that the things they summon are not under their direct control, and instead are controlled by the GM.