Azol's Green-Flame Wreath

You evoke green flames in a 10-foot Emanation centered on yourself for the duration, granting the following benefits:

• Creatures within the spell's area have Resistance to Cold damage.
• Any ranged weapon attack that passes through the spell's area is made with Disadvantage. On a miss, a thrown weapon begins Burning, and a piece of ammunition is destroyed. On a Critical Hit, the attack deals an additional 4d8 Fire damage.
• Whenever another creature enters the spell's area for the first time on its turn or starts its turn there, you can force it to make a Dexterity saving throw. The creature takes 4d8 Fire damage on a failed save, or half as much damage on a successful one.
• Once before this spell ends, when you deal damage to one or more creatures, you can deal an additional 4d8 Fire damage to each of those creatures. This spell then ends.

Using a Higher-Level Spell Slot. The damage increases by 1d8 for each spell slot level above 4. With a spell slot of level 8 or higher, creatures gain Immunity, rather than Resistance.