What to know
Krigen has 1,300 health and spawns in the Meadows, the swamps, the mountains, Black Forest, the plains, the Ashlands, the Deep North, the ocean and the Mistlands.
It resists pierce and frost; poison does nothing to it at all. Blunt and slash land at full damage, so that is what to bring.
Of everything craftable, 
Lightning Strike, 
Thunderblood Sledge and 
Thunderblood Greatsword put the most damage through what it resists.
It always drops 
Leather Straps.
Spawn command
With devcommands enabled, this spawns Krigen in front of you. The third number is the level: 3 spawns a 2-star.
Creature ID: JotunWarrior · all console commands and IDs