Auril (The Frostmaiden)

The goddess of Winter, Auril the Frostmaiden, who is the BBEG of "Icewind Dale: Rime of the Frostmaiden" adapted to function as a patron to a Warlock. The Warlocks who have Auril as their patron gain powerful ice magic, abilities and spells to influence the weather, the ability to turn into an Owl and some protection from potentially leathal damage.

The Warlock might be a devoted follower or priest of the neutral evil godess. Alternatively the Warlocks could have siphoned some of Auril's power into themself either by accident or with intend. As with any patron the exact way in which the Warlock gained his or her magical abilities is entirely up to the player's creativity in the backstory.

Warlocks of Auril gain access to an extended spell list, which is mostly combat orientated, similar to the fiend. However, most of the abilities granted by this patreon are focused on utility in a cold environment. Even at the lowest levels Auril's Warlock is rather unbotherd by the cold. With higher levels the Warlock gains the ability to create the enviorment for which he or she is best suited.

While this subclass is decent at doing it's part with damage in combat, it excells at branching out into a support caster while doing so, either by keeping party member safe from falling unconscious, trapping someone in a tomb of ice or turning the weather in the party's favor.

Expanded Spell List

Auril lets you choose from an expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you.

Auril Expanded Spells

Spell Level	Spells
1st	shield, ice knife
2nd	snilloc's snowball swarm, skywrite
3rd	sleet storm, animate dead
4th	death ward, ice storm
5th	cone of cold, hallow

Reborn in Ice

Starting at 1st level you have immunity to cold damage, you ignore difficult terrain caused by snow or ice. Frigid water has no effect on you. Snowfall, blizzards, fog and rain don't obscure our vision or affect your perception negatively. You have advantage on stealth in these weather conditions.

You can cast the "Ray of Frost" Cantrip at will.

Eternal Winter

Starting at 6th level you radiate frigid cold. In a radius of 100ft of you all creatures without resistance or immunity to cold damage suffer vulnerability to cold damage.

Additionally you can change the weather to arctic conditions (Casting time: 1 minute). This weather causes freezing temperatures and heavy snowfall which obscures sight beyond 100ft. After 10 minutes of snowfall the ground is coverd in snow and considered difficult terrain. You can only change the weather if you are outdoors. The arctic weather remains for 1d8 hours and has a range of 1d4 miles. This ability can only be used once and must be regained by a long rest.

Frozen Wrath

Starting at 10th level you can cast a magical blizzard. All creatures within 30ft of you must succeed on a Constitution saving throw of DC15 + your spellcasting ability modifier, or they are petrified in ice and suffer 4d6 cold damage. Upon a successful saving throw against the initial casting the creature is pushed back 5 ft and suffers half the damage. A creature can break free from the ice if it succeeds a DC15 Constituion saving throw at the start of their turn. Every turn a creature starts in this frozen state, it takes 1d6 cold damage. This ability can only be used once and must be regained by a short rest. 

Auril's Tomb

Starting at 14th level, you can cast Wall of Ice as if it were cast with an 9th level spell slot. This Wall of Ice has an AC of 18 and 50 hit points per 10-foot section.

Once you use this feature, you can’t use it again until you finish a long rests.