The most dangerous was an aura, called by some sages a mind freeze aura, of cold that could daze or even stun other creatures; the aura could be suppressed by the Frostwind virago at will. 

The Aura is, at full range, a 15ft sphere around you.

The Wisdom Saving Throw for this is 17.

They could also conjure a whirlwind, 30 feet (9.1 meters) in diameter, of ice shards around themselves for protection.

(For Ice Storm-convert the bludgeoning damage to Piercing)

When the Frostwind Virago spoke and willed it so, she could charm creatures within 300 feet (91 meters) of her, compelling them to walk straight towards her.

Suggestion-The creature doesn't need to be able to understand you but has to speak at least 1 language and the range is 300ft. The Wisdom-Saving Throw for this 17.

Frostwind viragos could naturally fly through their innate magic, and were also capable of swimming even in the coldest waters.

Frostwind Viragos are almost always Neutral Evil. Although there are a few Chaotic Neutral ones

Frostwind viragos were about 5 feet (1.5 meters) tall. Your size is Medium.

Accustomed to blizzards and many dark days and nights you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.

You have proficiency in the Perception skill.

You have advantage on saving throws against being charmed, and magic can’t put you to sleep.

Frostwind viragos were immune to all effects of the cold, for they themselves were so cold that even fire was not dangerous to them; only cold iron was.

Your touch freezes water and blood. Any humanoid close to you will feel a drop in temperature. Torches or small fires too close to you will be put out.

Frostwind Viragos don’t need to sleep being fey. Instead, they meditate deeply, remaining semiconscious, for 4 hours a day. While meditating, you can dream after a fashion; such dreams are actually mental exercises that have become reflexive through years of practice. After resting in this way, you gain the same benefit that a human does from 8 hours of sleep.

You can speak, read, and write Common, Sylvan, Auran, and Elvish.