Bianca's Frigid Radiance

Using magical flames you burn 12 rose petals - half of them black, half of them white. Following this, a bright blast of magical energy bursts from you in a 30-foot radius. Any creature within that area must make a Constitution saving throw. If a creature fails this saving throw, they take 5d8 cold damage, 5d8 necrotic damage and have their speed halved until the end of their next turn. If a creature succeeds on the saving throw, they take half damage and their speed isn't reduced.

At Higher Levels. When you cast this spell using a spell slot of 7th level or higher, the cold and necrotic damage increases by 1d8 for each spell slot level above 6th.