Your technique is beautiful in its simplicity: the ability to make and control ice.
Cursed Energy
Starting at 1st level, you can harness your negative feelings into a usable source of energy called cursed energy. These feelings can be harnessed into attacks or abilities. The amount of cursed energy you possess is based on your class. Some classes use either Charisma or Wisdom as a modifier (player’s choice).
Your Cursed Energy DC is 8 + your Cursed Energy modifier + your proficiency bonus.
Ice Creation
Beginning at 1st level, your innate technique allows you to interfere with the temperature around you, creating extreme levels of cold. As an action for 1 Cursed Energy, you can force every creature in a 10-foot cone to make a Dexterity saving throw. On a failure, they take 1d10 cold damage and are restrained as ice covers part of their bodies. On a success, they take half as much damage and are not restrained.
The creature may make a Strength saving throw at the beginning of each of its turns to break the ice and end the restrained condition.
All ice created by your technique lasts until you end it at will, a creature breaks it, or you gain the poisoned, paralyzed, stunned, petrified, or unconscious condition.
At 3rd level, the damage of this feature increases to 2d10, to 3d10 at 6th level, to 4d10 at 10th level, to 5d10 at 14th level, and to 6d10 cold damage at 20th level.
Extreme Cold
At 3rd level, being stuck in your ice feels like staying on a cold mountain while you wait for death. A creature inside your ice suffers one additional level of Exhaustion. Any creatures within 5 feet of your ice that don’t have cold resistance or immunity have their movement speed halved.
Frost Calm
When you reach 6th level, you have learned how to unleash thick layers of ice through the mist. As an action for 4 Cursed Energy, you can send a cloud of freezing mist to a spot within 60 feet of you. Every creature in a 30-foot-radius circle centered on that spot must make a Dexterity saving throw. On a failure, they take 7d8 cold damage and are restrained by the ice layer formed in their square. On a success, they take half as much damage and are not restrained.
The creature may make a Strength saving throw at the beginning of each of its turns to break the ice and end the restrained condition.
Ice Fall
Once you reach 11th level, you learn a great execution method that makes sure your enemies won’t escape. As an action for 8 Cursed Energy, you become prone until the beginning of your next turn to create ice on the ground. You telepathically manipulate the ice created, launching one piece at each creature of your choice within 30 feet of you. Make a cursed energy attack roll; on a hit, they take 1d10 cold damage and become restrained.
The creature may make a Strength saving throw at the beginning of each of its turns to break the ice and end the restrained condition.
Hit or miss, giant spikes of ice fall from the sky on top of the targeted creatures, forcing them to make a Dexterity saving throw. On a failure, they take 6d8 cold damage and 6d8 piercing damage. On a success, they take half as much damage.
Domain Expansion: Ice Age
If you achieve 18th level, you hone your technique to a fine edge, allowing you to use your Domain Expansion. While inside it, every creature except you must attempt a Constitution saving throw at the end of each of their turns. On a failure, they take 10d8 cold damage. On a success, they take half as much damage.