Prismal's Reversal

This enchantment reverses the relative velocity of an object or creature that passes through the affected portal. The spell can be cast only upon an area bounded on four sides by a solid frame, such as a window or a door. The spell cannot be cast on a portal smaller than 3 feet by 4 feet or larger than 18 feet by 24 feet. Creatures running or objects flying through the portal lose velocity, while those moving slowly are accelerated.

The chart shows the time required to pass through the spell's effect compared with movement rates. Once into the portal, a creature cannot withdraw or take any other actions until the portal has been passed completely. If passing through the portal takes a round or more, a creature caught in the frame loses any defensive Dexterity benefits until it clears the portal.

Prismal's reversal is resistant to the dispel magic spell. This has a 1% chance per level of the caster to negate the reversal. Physically destroying the frame ends the spell immediately.

Prismal created this spell as a theft deterrent. Since thieves are apt to run from an establishment, this spell makes them easy to catch (a full-speed sprint can be five times the standard movement rate).

The material component is a set of four matched ornamental stones, worth 400 gp in all, which are inset in the portal's frame. They crumble to dust as the spell is activated.