I have no idea if this thing has anything to do with Wintertusk but I am hoping that this spell could make it or something else based on it. Feel free to reply to this and if you thing it is bad, please state why. So here are my ideas based on Celestia and the bosses.
Fire: Astraeus Effect: 810 Fire Damage to all enemies and -90% Incoming Damage (shield)
Storm: Ptolemos Effect: 900 Storm Damage to all enemies and remove all traps from self (includes shields)
Ice: Frost Protector Effect: 920 Ice Damage and -20% Damage Aura to self for 4 rounds (Fortify except it is 20%)
Balance: Mithraya Effect: 800 Balance Damage and Dispel next spell
Death: Morganthe Effect: 600 Death Damage to all enemies and swap half to heal and -50% Heal
Myth: The Chanter Effect: Remove 1 Positive Ward (shield) and 750 Myth Damage to all enemies
Life: Superior WildClaw Effect: 920 Life Damage and +30% Dragon Blade to self (alternative to Dragon Blade could just be Guilding Light, +30% Heal)