Combination of Carthak

You use a powerful magic to cast 3 spells of the same level or lower all at once to create an effect that, when used correctly, can level battlefields or bolster allies. You cannot use the same spell more than once in a combo regardless of leveled slots. The spells you choose to combine will use their respective slots, for example, you cast [spell]fireball[spell/], [spell]magic missile[spell/] (lowest level), and [spell]counterspell[spell/]; you would expend two 3rd level slots and one 1st level slot along with the level slot you are casting this spell at.

At Higher Levels: When this spell is cast at higher levels, you can cast spells lower than that level.