While browsing through the old TeamXbox website using the wayback machine, I came across a game called "Dark Shores". Doing a quick google search didn't appear to have any information, but what's interesting is that the information on the Team Xbox page mentioned that it was formerly known as "The Druid King". Searching that up led me to a Gamespot article titled "The Druid King becomes Celtic Kings" ( www.gamespot.com/articles/the-druid-king-becomes-celtic-kings/1100-2862698/ ). I think this is just a coincidence however, which I'll explain further.
Team Xbox had two images of the game, reverse image searching both didn't show me any other results.
Here are the two screenshots I found:
Unfortunately the last photo only had a thumbnail available so it's not as easy to see.
Anyway, the reason why I don't think this game has anything to do with Celtic Kings is both for the fact that the gameplay is different and the developer is different.
Here's a link to the TeamXbox page, it has a description for the game as well