Chromatic Surge

You build up a reservoir of energy in front of you. On your turn, as a bonus action, you may roll a d6 as many times as you wish. Each time you roll, keep track of the total energy being increased by that amount. You may mix different energy types. If the total energy exceeds 10, then the spell backfires and you take damage equal to the energy stored. You may also decide to dispel the spell by hurling all the energy outwards with a distribution of your choosing. If the total equals 10, the damage is dealt immediately with a distribution of your choice, but doubled. The limit then increases by 10 and no energy is expended.

Every turn, the energy limit increases by 10. Failure to maintain concentration results in the spell evenly dealing damage to every possible target in range, including you, where you take 1d8 extra psychic damage. Surrounding creatures may, on their turn, attempt, as a bonus action, to add energy to the reservoir with an intelligence check with DC of your intelligence score. Upon success, they may perform the same actions, but the spell could backfire on them instead.

If the reservoir ever explodes, targets must make a Dexterity saving throw contesting your spell save DC taking half the damage dealt on success.

Using a Higher-Level Spell Slot. The limit increases by 10 more every turn for each spell slot level above 4.