Slick is an exclusive metablast; it does no immediate damage and has none of the normal effect of a blast. Instead, you set up a near-frictionless slick with a diameter equal to your Magic in meters, that will hinder the movement of anyone inside it.
The slick is clearly noticeable, but transparent, and lasts until the end of the Sequence. The puddle has no game effect after the end of the sequence, but is still there and still foul until cleared away. If you spend a Magic point it lasts until dispersed (at least a few minutes).
Anyone in the slick must make an Agility task check with your Magic as the difficulty in order to avoid taking a fall. Any movement or actions contemplated automatically fail in this case. Damage Immunity to Water or Earth rather than Blast protects against this.
An exclusive metablast has none of the normal effects of that blast, including any other metablasts that would ordinarily apply. In effect, an exclusive metablast is a separate effect that replaces what the blast normally does. Still, it takes it's appearance from the blast it is used with, if it does any damage it is of the same type, and a Damage Imunity that would protect against the blast also protects against the exclusive metablast.
If you can only use the blast to create a slick, and cannot use it for plain damage, this metablast schtick is free.