To put some stuff into perspective I have looked into the utilization of language and context.
So far We have
Orkney Island (referenced in game to be home of Findan) which historically is an island that was temporarily over run by nords around 875AD though settlements of the area predate into the mid 6000BCs
We were also briefly introduced (via story) to the son of a man named
Findan which has multiple roots in ancient/proto languages from the
saxon periods which range from the 5th-12th centuries (401AD-1200AD)
Given that Orkney island was only influenced by the nords historically in the the 800s we can use that as a starting point. cross referencing it with the name of the father which falls between the 5-12th centuries we can conclude that this is historically feasible.
In the dusk of the 8th century being the year 800s we enter the
post-classical time period before the 14th century that ushers in the renaissance, though
Late Antiquity can sometimes be factored in.
We can see that given Orkneys routing by the nords in 875 that we were on the brink of the 9th century. cross referencing that time period with the
life expectancy chart we can see that classical rome which was around during late antiquity has an av life expectancy of 20-30 years of age.
Given the earliest of 875, Assuming longest life span possible Findan having a son at say 25 would bring us to the year 900. His son growing until also around 25 and meeting Senua bringing us to the year 925 the protagonist whom is already around 20 brings us to Senuas probable DOB at the year 905AD.
to further substantiate this Senua Derived from the mis translation originally of the the celtic goddess
Senuna whos name etymology includes Senua which in addition to the original/correct spelling is rooted in
Proto-Celtic which lasted until the 8th century before becoming fully celtic.
but I dont have too much time on my hands.
but definitely looking for it!
29chf on STEAM .... i didn't expect that ... (tho still out of my budget for the 2 and a half next weeks 
)
