So far as I know, this is the only quest (and really the only thing ever) given by a knight in CastleVille Legends. Knights are generally very passive characters in this game, but I guess there was no better character to introduce the concept of Alliances, since knights are a key feature of alliances. This is a two-part quest, is given as soon as you level up to Level 10, and could take a while to complete if you haven't yet had a chance to start exploring your kingdom.
Note to Part 1: When expanding to the Embassy ruins, I recommend getting there by way of the curved wooden bridge, since this will mean you've already knocked out one of the requirements of Glurb's Feed the Troll quest when you reach it at Level 15.
Part 1 of 2:
Part 2 of 2: