Binding Trial by S. B. Sebrick

Prince Labek's people face extinction. The barbarian tribes struck as one, cutting down the capital city and his entire family in a matter of a few bloody hours. Now all that remain is a small number of survivors desperate for a power no enemy can match.

But the 'Binding Trial' requires two candidates and if finding a powerful princess weren't issue enough, the price of failure will include the death of every remaining person Labek holds dear.