It's early Modern English not Old. Old English is the language of Beowulf.

Hwæt. We Gardena in geardagum, þeodcyninga, þrym gefrunon, hu ða æþelingas ellen fremedon.

Micel mē þynceð þanc, þæt þū gemanst

mǣl-gespreca ealdra.

Wæs þū hāl.

Also known as a royal plural

It's a possessive, right? I.e. "Your Majesty's most humble and most obedient servant and subject?"?

Ultima games incorporate archaic language constructs in their dialogues and texts, but they are fictionalized rather than historically informed. I call it "langfic" (as in "fanfic"). The French edition of U7 is also notorious for featuring old vocabulary, but does so mixing up constructs from different eras and reforms. While the effort on the English edition is much more convincing, I wouldn't bank on it as a reference of its use; instead, I would turn to more scholarly sources that examine Early Modern English in depth.