Gah! That's my first honour mode attempt ended in failure at level three in the Whispering Depths. I accidentally triggered the Spider Matriarch fight when I'd just been sneaking around destroying her eggs and was intending to then go away and rest up before the battle - I thought I'd got away when suddenly she and the two phase spiders came phasing after me and cornered my party in a really inconvenient place, and given their mobility there was no fleeing the combat. I still might have got one of my party away had I realised that her legendary action wouldn't necessarily mummify the same individual who attacked one of her children, but could entomb another of the party instead.
Ah well, I'll know for next time. And I'll probably carry on this run anyway as I do like the character.
(I do wish it was possible to turn off single save mode after failing but continuing an honour mode run, but doesn't look like it is.)