Cold-Acclimated

At 2nd level, you can exist comfortably at temperatures as low as -50°. You ignore difficult terrain caused by ice or snow. You have advantage on Intelligence (Nature) and Wisdom (Survival) checks in cold environments.

Secret of Rimefire

Starting at 2nd level, you learn how to use rimefire. Rimefire appears as pale blue flame that chills rather than burns. It can freeze water like normal cold magic, but can also ignite substances that normal fire can. Instead of charring such substances, it damages them by transforming them to ice. It can be extinguished like normal fire.

Whenever you cast a druid spell that normally deals cold damage or fire damage, you can make it a rimefire spell. Rimefire spells deal cold damage.

All spells from other classes that deal only cold or only fire damage are added to the druid spell list. You may prepare them as druid spells. All spells you prepare this way are rimefire spells.

You can add your Wisdom modifier (minimum of +1) to the damage roll of any rimefire spell that you cast. The damage bonus applies to one damage roll of a spell, not multiple rolls.

Finally, you learn Produce Flame and one other cantrip from any class that deals cold or fire damage. They are rimefire spells and don't count against the limit on the number of cantrips you know. You can also spend an action to manipulate rimefire as if with the Control Flames cantrip.

Frozen Flame Power

At 6th level, you gain resistance to cold damage. Your rimefire spells ignore resistance to cold damage.

Rimefire Creations

Beginning at 10th level, you can create objects out of solidified rimefire ranging from flawless sculptures to bridges. Each minute you spend doing this, you create up to 1 cubic foot per druid level of solidified rimefire in precisely the shape you desire. Between long rests, you can create as much solidified rimefire as you could in 5 minutes.

Objects made of solidified rimefire have immunity to cold and resistance to fire. They are as hard as wood and unpleasantly cold to the touch for most creatures. They appear to be made of ice, but have an inner glow. They only start melting above 80°. This means that depending on the climate, you could over time create structures of great size.

As an action, you can manipulate solidified rimefire in ways similar to how the Move Earth and Shape Water cantrips allow manipulation of earth and water.

Frozen Flame Mastery

Starting at 14th level, your rimefire spells treat creatures immune to cold damage as if they instead had resistance.

Rimefire Rush

At 14th level, you can dash around the battlefield while igniting your foes. As an action, you can expend a use of Wild Shape to turn into pure rimefire and move up to your speed. This frees you from being grappled or restrained. This movement does not provoke opportunity attacks and ignores difficult terrain.

While moving, you can pass through a space as narrow as 1 inch wide without squeezing. You can also pass through other creatures. Any creatures you pass through must make a Dexterity saving throw against your spell DC. Creatures that fail take cold damage equal to your druid level and catch rimefire; until someone takes an action to douse the rimefire, the creature takes cold damage equal to your Wisdom modifier at the start of each of its turns. Creatures that succeed take half damage and do not catch rimefire.