GM Thoughts on Hommelstaub
Played effectively, Hommelstaub would be impossible for a party to fight - at least under normal circumstances. If he were used for the Ambush against the party the night before, then there is a significant balancing of the scales (as Hommelstaub may be able to see through snow but it being night does cause him the same problems many PCs would have (he has low-light vision and it's overcast at night).
Given the fact "heavy snow" is falling (I went with blizzard to reduce the visibility of the group and create a more claustrophobic feel to the fight - and having Teb looming out of the 20-foot range of sight for the group did ramp up tension for the players), it actually makes sense to have reduced daytime visibility for Hommelstaub (and for that matter the adventurers). Then again, if they'd chosen to attack at night, it would have allowed for a stealthier approach to the Portal.
Still, I have no regrets having Hommelstaub slain by the Black Rider. My depiction of him is of a strong powerful warrior who continues to move by force of will (and Baba Yaga's favor). Part of me is actually tempted to give the group a touch of Mythic - have them only die when they reach double their Constitution bonus, and automatically stabilize.
The amusing thing is, if this had been a level 2 group and I'd not modified Teb to have a level of Unchained Barbarian, then he honestly would have fallen probably after two rounds of combat. My players had some really lucky damage rolls. I'd have been left with the same problem with Hommelstaub however - a sniper who can attack from beyond the visual range of the players. And once the players got within melee range, his ability to go invisible and flee just made him into a true aggravation. Given the hour we were at and the fact I honestly didn't want to delay yet again having the Black Rider appear... using him to end the fight was for the best.
Besides. The game is about having fun. Of the six members of the group, only the Barbarian was at half hit points. Everyone else was within four hit points of being full up. All Hommelstaub would have been was that annoying final foe that is sniping you from a hidden location that you find in the occasional video game. It's better to just cut-and-run in those cases.