Still in Act 1, so no spoilers please.
I found out that if you have the Idol of Silvanus in your inventory and transfer it between characters while in sight of the Strange Ox, the entire herd aggros and attacks you. Cue the speculation!
Edit: Did some testing, apparently all the tieflings react the same way, so it’s not some scripted event for the ox :(
oh, cool! Gotta get a move on then. My merry group of murderhobos have been parked for a week or so on front of some weird shadow place which hurts