Writing is about reading, investigation, and fact finding expeditions. The internet has given writers a one stop shop to look up history, science, and even science fiction. When writing a historical character, a write needs as much in depth knowledge of that era as possible.
In the case of Hode, Roben is a modern version of the mythical persona. So the legend is more of a set of guidelines than rules. However, supporting characters like Marian can have ties to the past as much or more than a modern retelling's protagonist. Marian in the first novel states she has family ties to the old Celtic ways of magick as a priestess. These characters usually have tattoos or brands, one of which Roben notices on Marian.
So what does a writer do for the second novel? Well she researches the Ogham. Ogham is a series of lines that equate to the phonetic alphabet. We write in English which is denoted in Latin characters to convey our message. Lines like Runes and the Ogham did the same thing when reading and writing was less necessary or available to the public.
But I like taking the concept to the next level. I not only translated my character's information to Ogham, I looked up the Ancient Celtic word for the item I wanted translated.
So in modern vernacular, Blood is fuil in Gaelic. Fuil is this set of marks in the Ogham:
Will this be of use in the next novel, I hope so. Research takes hours and sometimes days/weeks to complete on something as simple as an ancient word and its non-Latin transliteration.
Luckily research into the past can be done online instead of in a room full of musty, dusty tomes.
What research have you conducted to create depth in your character's backstory or plot point?