That is the gist of it. [To keep it in simplest possible terms.] I did say it was a hard to believe tale. [His tone was weakly jovial like he struggled to make any sort of jest from this. Especially with that follow up question that left Diarmuid quiet and made his expression go from neutral to a bit of a frown.]

A War to win the Holy Grail. To have it grant any wish of the victor.