SPOILERS ARE CONTAINED WITHIN REGARDIN ELDEN RING.
So a long-lived and stubborn pseudo-archaic typo is thyselves, itself an erroneous plural form of thyself, where the proper would be the yourselves, since it is literally the second person plural that is supposedly being used.
Case in point, a quote from Elden Ring, at a point where one of the main characters quotes Marika, a divine queen, and mother to the bosses of the game:
"In Marika's own words. Hear me, Demigods. My children beloved. Make of thyselves that which ye desire. Be it a Lord. Be it a God. But should ye fail to become aught at all, ye will be forsaken. Amounting only to sacrifices..."
Now, what strikes me as even odder is the addition of "ye", the correct second person plural in the subject case, whereas "thyselves" at the same time in its malformed case apparently take on the role of a tushery-esque "yourselves."
What is the line in the original Japanese version then? Anything resembling the archaic diction if incorrect in the English version?
Let us take a look,
...Marika no kotodama o, sonomama tsutaeru
Demigoddo, waga itoshiko tachi yo
Omae-tachi ha mou, nanimono ni nareru. Ou de are, kami de are
Soshite, nanimono ni mo narenu toki, omae-tachi wa misuterareru
... Soshite nie to naru noda
"Thus conveyed are Marika's numinous words,
O my beloved children, Demigods.
Whatever ye want to become, be it rulers or gods.
And if ye fail to become anyone, ye will forsake yourselves
And shall become a sacrifice."
"Omae-tachi" (you [plur.]) is not archaic, rather it's informal and fits a mother talking to her children - and the grammatical number.
What is archaic is her usage of the verbal negation nu, rather than the modern nai, Nevertheless her using waga itoshiko uses the archaic if formal waga (my/mine) rather than watashi no or any other modern genetive construction.
Of other linguistic note is that the Japanese word kotodama (言霊, lit. "word spirit" or "language soul") is used translated/localised in the English version as "own words" and elsewhere as "spoken echoes", which on one hand completely skips entirely the word's Shintoistic connotations - which on the other hand and to be fair is a difficult word to find any one English translation for, which is why "spoken echoes" is one way of conveying kotodama's nuances of mysteriousness that it may have for the Japanese gamer.