Any writer of historical fiction has a decision to make before they commit a single word to paper: how will their characters speak? The more distant the era of their story, the tougher the task before them. We want our characters to be credible and we're aware that language is constantly changing - listen to this recording of how a medieval prince might have sounded - but we don't want to over-tax our readers with archaisms.
Personally I've never dared venture further back than the 18th century. I take my hat off to those who recreate much earlier times, particularly if their novels are set in the heyday of minced oaths. It must be a finely judged thing, whether to drop in the occasional 'gadzooks'.
It is hard for us in these secular times to comprehend the depth of religious faith and practice in earlier centuries. Its thread ran through every aspect of daily life and blasphemy was taken very seriously indeed. 'Sblood was a fairly blatant contraction of 'by God's blood' and Shakespeare used it a lot.
'sblood, do you think I am easier to be played on than a pipe?' - Hamlet, Act III, Scene 2, to give you but one example.
'Zounds' was another early oath, presumably first pronounced to rhyme with God's wounds and then metamorphosed to rhyme with 'hounds', perhaps during sterner Puritan times. The 1606 Parliamentary Act to Restrain Abuses of Players made theatre companies more careful about the oaths they spoke on stage. A 'bloody' might cost you a fine you could ill afford.
The use of 'egad' (Oh God!) didn't become common until the 17th century, and 'ods bodikins' - another highly minced reference to the nails of the cross, like 'gadzooks' - appeared later still, in spite of its antique flavour. And of course language, as constantly changing as a river, still comes up with oaths suitable for tender ears or religious sensibilities. 'Dog barnit' is one of my 20th century favourites, a gentle expletive I think you'll agree, when all the world is effing and jeffing like there's no tomorrow.