Larian Studios Forums Baldur's Gate III Baldur's Gate III - General Ways to break Oath of the Ancients

I tried this Plagg, Nik-Nuk, and Crub fight some more times and figured out the trigger:

If Wyll has joined you but isn't in your party when you kill PNC, the game breaks your oath -- regardless if you've ever talked to Wyll at camp or adventured with him. I reloaded, added Wyll to my party, talked to him at camp, and had him with me to kill PNC. Oath remained intact.