This guy took quite a lot of time to spawn. I estimate around 20 kills before he did (so approximately 5% spawn rate.) The locations given below (944, -203) are accurate. Sometimes there are two placeholder bears, sometimes there are three. Mine spawned on a 'triple cycle', and he dropped the spear.
Take care using AoE in the space leading to this little alcove as it may aggo Lady Vox and her retinue. Interestingly, AoE didn't do so in the bear alcove itself.
Anyway if you wanted to fight Lady Vox without all her minions, that might be a way to do so.
Spawn rate on placeholders is 15 minutes.
Edited, Jan 9th 2022 4:34am by IsaacN