the Legend of the Deep - Episode IV

A group of abnormal reproducing monsters poses such a great threat to the continent that kingdoms stop rivalries to oppose them. The mightiest state suddenly gets defeated by the beasts, so princess Sofia is going to be crowned queen-in-immigration. But Sofia and her followers get lost on the way in an ancient archaeological site.
A group of knights is sent there to discover the princess' fate.

[From vndbreview]