Frost Wisp
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What to know
Frost Wisp has 100 health.
It takes extra damage from fire and spirit; it resists blunt, slash and pierce; frost and poison do nothing to it at all.
Of everything craftable, 
Lightning Strike, 
Staff of Embers and 
Thunderblood Crossbow put the most damage through what it resists.
Spawn command
With devcommands enabled, this spawns Frost Wisp in front of you. The third number is the level: 3 spawns a 2-star.
Creature ID: FrostWisp · all console commands and IDs