Chell’s Mystic Apertures

You create linked teleportation portals that remain open for the duration. Choose two points you can see within 60 feet of each other. Each point must be on a relatively flat, solid surface large enough to accommodate a circle with a diameter of 5 feet. A circular portal, 5 feet in diameter, appears on the surface in both locations, oriented parallel to the surface. An unwilling creature about to fall into a portal must succeed on a Dexterity saving throw to avoid falling through.

Any creature or object entering a portal exits from the other portal as if the two were adjacent to each other. As things pass through the portals momentum is conserved, and spells excluding Chell's Mystic Apertures can be cast through the portals. Creatures, objects, light and spells pass through from one portal to the other as if it were a doorway. This may allow for non-standard Line of Sight situations. You can take an action or a bonus action to change the target point of one of the portals to another valid location within range you can see. Taking an action and a bonus action allows you to move both ends of the portal in the same turn.

If an individual creature or object passes through the portal three or more times in the same turn, the portal becomes unstable and the spell ends.

When the spell ends or an end of the portal is moved, objects midway through the portal are forced out of the nearest side, or a random side if they are at the midpoint.