The Burning Colossus Plate -- 5th and final relic of the
Legend Regarding an Old Map Treasure Hunt theme's 2nd relic route. It can only be discovered in the
Sea of Wonders off Candia, and requires:
Archaeology R13
Recognition R11
Greek language (skill or aide required)
Note that you must enter the Sea of Wonders and clear the entire SoW in order to find this relic. If you don't have a full fleet, race as fast as you can for the exit star each time, and you should succeed.
Also, keep in mind Alnr's warning: "The final relic is located in 4th/Final section of Sea of Wonders, where you can't use translation notes and whatever. So it is likely that you must have that language skill. You can use aide's language skill however, i'm not sure it can be leeched by your fleet members, especially on Sea of Wonders."
Note that this TH does not drop a special item like most THs tend to do. Shame. Cheers, and happy relic hunting to you.
Source: gvdb.mydns.jp/db/module/QuestDB/action/QuestShow?id=3443
Credit to: Caro for the relic name.