I have seen a translation of it somewhere before....the premise is very very interesting.
Archer is Gilgamesh, THE Gilgamesh we know
Berserker is Jack the Ripper, but the paradox is that, because Jack was a true psychopath during his life time, making him into a Berserker actually turned him sane, lol. So, here we have a cool, calculating Berserker who still has the status bump.
Rider is the Black Death. It is kind of confusing, but Rider is the materialization of the Plague, a concept. Think of it like Wallachia. This Rider rides humans.
Caster is a French novelist, all the fantastic things he writes become true. So all he does is write about powerful Noble Phantasms for his masters...
Assassin is a "failed Hassan", who strangely knows the Zabaniya of ALL Hassans.
And Enkidu is also a servant here, who looks like a trap.
These are all the fragments of the information I can remember from the top of my head... I am very sure it is not a full novel, more like a role play starting kit.
Are we Beast's Lair Lite? Are we?!