Fimbulveter

Description
Upon casting, all enemies are inflicted 1 every second over the next 6 seconds. This totals to 6 Frost being applied, or 2 triggers of Frost damage. Since the Frost application is unavoidable and cannot be interrupted in any way, it is bare minimum 300 damage dealt to all enemies.

Strategy and Synergy
This is a powerful one-time use spell (for each battle) that is effectively worth 6, making it a value pick that also ignores the need for the player to shuffle their deck. Since no additional inputs from the player are required other than simply having the to cast it, it is very easy-to-use and doesn't consume much of the player's attention which is better off trying to dodge enemies' attacks or to use other spells in tandem. The wide-ranging Frost application allows this spell to synergize especially well with Frost artifacts, such as which will heal the player for 40 HP per enemy, or, refunding the Mana required to cast this spell completely as long as there are two available targets. doubles all of the above as long as the player is inflicted with.

Fimbulveter is universally a good spell in any deck because of the already high amount of damage that it does even without any synergies, and a must-take for any Frost-based archetypes should it happen to be offered. However, due to its Calamity rarity, it is generally not advised to focus solely on getting it.