Best answer
SnowGlobeFinder
Quick tip: just grab a Snow Globe after beating down some Frost Moon enemies. Use it, and boom, Frost Legion time!
All answers
WinterWanderer92
Summoning the Frost Legion is a wintry blast! All you gotta do is find yourself a Snow Globe. You can snag these precious globes by defeating any of the Frost Moon's waves - they often drop from presents during the Christmas season (December 15th to 31st). Once you've got one, just use it in your inventory, but make sure you're ready for a chilly showdown!
ChillOutDude
Honestly, why bother? The Frost Legion is just a hassle. Spend your time building something cool instead.