Aspect of the Lightning Stag
Aspect of the Lightning Stag has 3,000 health.
Nothing but a player can damage it, so tames, Dvergr and summoned companions do nothing for this part of the fight.
Its hardest hit is antler at 150 pierce, out of 3 attacks.
Some of what it throws is elemental, so lightning resistance is worth having.
Aspect of the Lightning Stag is a phantom copy of 
Eikthyr that 
Kall Fimbulbringer summons during his second phase. At 3,000 health it is by far the largest of the seven aspects, nearly twice the next one and six times the health of the real Eikthyr in the Meadows. It has no resistances or weaknesses of any kind, so every damage type lands at full value, and it runs at 8. Only player damage registers on it.
It is the only aspect with no resistances at all, so whatever you brought for the King works at full value here. That combination, biggest health pool and zero protection, makes it the one worth spending a real cooldown on. Both of its heavy hits are pure lightning, so the fire and frost resistance you packed for the third phase does nothing about them.
With devcommands enabled, this spawns Aspect of the Lightning Stag in front of you. The third number is the level: 3 spawns a 2-star.
Creature ID: Aspect_Eikthyr · all console commands and IDs