Arcane Overcharge

As a Wild magic Sorcerer, one that had tampered with an immensely raw form of untamed powerful magic. Rune can tamper with the forces of chaos and overcharge the magic within himself and his allies. He can target a single creature, giving them a magical disease that is incurable, and cause it to be immune to all damage until his next turn. All damage dealt with that creature is stockpiled within their body, visually, the creature glows an array of vibrant colours as the magic begins to fester, intensifying, and amplify. On Rune's next turn, he can use his action to cause all the damage that was supposed to be taken and was stockpiled in that creature deals double damage. Rune can only use this semblance once every 1d4+1 days and after using it, he gains 1d4+1 levels of exhaustion.