This is the boss owlbear. She spawns only when the Owlbear have won every position in the Moor: North Caves, East Cave, and South Swamp. After winning all of those, the owlbear take over the Vah Shir outpost and she spawns in there, always. No placeholder, she is there from when they take it over.
you could solo this boss, but you couldn't solo the things you have to kill to get this boss to spawn. they're perma rooted, but they summon you and hit you then. wait till you're lvl 55+
65 Rogue here, easily soloed entire war with only self buffs. Owlbears took over outpost and I waltzed right in. All attacked, but most hardly hit. This one however did make a dent in my HP, but nothing to sweat about, 30 to 40 seconds later the war was done. No problem. Dropped the beak.
You have to have the owlbears to rule all 3 camps (owlbear cave, sonic wolf cave and the grimling camp).. just kill the boss at those places (sonic wolf and the grimlings) and help the attackers..