A rift in space which fits into a 5-foot radius, 30 feet tall cylinder appears as space ruptures, causing wild elemental energies to spill forth into the world. When you cast the spell you roll a d8 to see what type of damage the rift deals until the start of your next turn:

When a creature enters the rift's area for the first time on a turn or starts its turn there, it is ravaged by the rift and must make a Constitution saving throw. It takes 8d6 damage of the indicated type on a failure or half as much on a success.

Roll a d4 to see how many blasts shoot out from the rift this turn. The rift has a pool of 12d6 which is split evenly across all the blasts (one beam of 12d6, two beams of 6d6, three beams of 4d6, or 4 beams of 3d6). Each blast can be directed at a creature or object you can see within 30 feet of the rift, and a given target can't be struck by more than one blast per turn. A struck creature must make a Dexterity saving throw, taking the appropriate amount of damage on a failure, or half as much on a success.

Until the spell ends, you can use your action on subsequent turns to cause more blasts to shoot out from the rift on subsequent turns, rolling as above for the type and quantity of the blasts.