Almost every Arcane Background has access to some form of “petty magic” - minor but versatile effects that can be produced at will. Wizards may call them cantrips, clerics may call them orisons, but they’re functionally the same for everyone. To cast a cantrip, you need only spend a power point to produce the desired effect.
Cantrips can have both superficial and mechanical effects - exactly what a cantrip does is down to the player and GM’s discretion. However, their effects should minor; they should not be as powerful as an existing power; and their effects should be temporary in nature. A good rule of thumb is the Elemental Manipulation power; if the desired effect is as strong as that power, then it’s too powerful to be a cantrip.
Generally speaking, cantrips can produce the following mechanical effects:
- Perform some minor action in line with the limitations above, like levitating a light object or cleaning your clothes.
- Give a +1 bonus to a single skill check - for example, by magnifying your voice for Intimidation.
- Allow you to make a skill check that wouldn’t normally be possible, such as using Thievery to pick a lock without lockpicks.
- Use your spellcasting skill to make a Test against an enemy.
When a cantrip is being used to make a skill check, it counts as part of the same action; so you don’t get a multi-action penalty from casting a cantrip and attempting the skill check. Otherwise, casting a cantrip is an action.