At the end of Bloody Path to Peace, you’ll need to tell Ivarr what happened to Ceolbert. At this point you’ll have three dialogue choices. It doesn’t matter which one you choose, as the outcome will be the same.
“It was the Britons.”
Eivor gives the blade to Ivarr, saying it was the Britons who killed Ceolbert.
“This means war.”
Eivor states that what happened to Ceolbert was done by the Britons, revealing the blade to Ivarr.
“We failed Ceolbert.”
Eivor states that they have failed Ceolbert, before handing the blade to Ivarr, indicating that it was the Britons who killed Ceolbert.