Chaos Portal

You open a ten foot diameter black portal to another, nameless dimension. Anything within the space of the portal must make a Dexterity savings throw to avoid the portal or be sucked within it, transported to another dimension (location is DMs discretion). Caster may choose the dimension if it is another plane of existence they have traveled to.

The caster may direct the movement of the portal up to a maximum of ten feet per round or may allow it to move randomly (roll a d4 for each five feet of movement; 1 goes north, 2 east, 3 south, 4 west; roll a d6 for hex maps) at thirty feet per round. All creatures must make a Dex savings throw EACH time the portal moves into their space, even if it happens multiple times per round.

Instead of moving the chaos portal the caster may opt to increase the size by an additional five feet diameter to per round up to a maximum thirty foot diameter.

The chaos portal can pass through solid objects but does not damage them and does not transport anything except creatures. If the creature is larger than diameter of the chaos portal AND passes the savings throw, it takes 6d8 slashing damage instead for each round it is in the same space as the portal.

The chaos portal cannot be stopped by anything less powerful than a wish spell. Caster may choose to end the spell early as a bonus action by making an Intelligence savings throw. If the caster is killed the portal closes early. The portal does not close early if the caster is transported to another dimension by the portal. Creatures may choose to fail their savings throw and be automatically transported to another dimension. Note: the portal can transport multiple creatures to multiple dimensions in the same round.