Gorgeous. It's tonally centred, with nothing leaping out as too highlighted next to a flat area. Solid colour choices for the bits supporting the whole, they reinforce the gritty realism angle.
Loving the smooth red. Though highlights could go a stage further on the most extreme areas. And a bit of weathering on the edge near the floor could be groovy.
The metallics are enriched by the subtle colours worked in there. Notably on the breastplate. Though, the picking out of the rivet/studs doesn't appear as clean as it could be. A strong dark tone worked around them, then picking out just the very top of the studs in silver would really make them pop.
The flesh is clean and smooth. Some cool colours in there too worked in various points. Looks quite waxy and ill overall though, rather than the yellowy-pink caucasian flesh they'd normally display.
That gore sure works. Looks, gory. Not sure about the bloody tendril though, doesn't seem to be falling quite right. Probably the length with a relatively weighty tip causing it to move just off the vertical. Reckon a short length could've worked better.
The scrolls around the arm could benefit from a mite more shading to give them definition. On the "from the back" shot, where they wrap under the arm to the gold studs and then hang down would be a good place to introduce some subtle darkness.
The writing didn't work out great eh. Pins and cocktail sticks can be useful in applying that kinda thing, though I've not had any success with them. Have used a technical pens for that, a cheapo disposable one at a 0.1 size.
Though a fine brush with ink rather than paint is what I go for. Ink just barely on the brush tip, so it ain't loaded allowing for a rush on ink to splurge.
Also, it ain't a bad idea to give it a go on paper first, so you can work out how much text and at what size can be written on.
For the big parchment sheet you can take inspiration from historical examples. Having a BIG initial in the top left starting the writing off, rendered with a complimentary colour aswell as the dark ink. Could also give it a decorative trim once you feel comfortable enough with that level of detail.
Overall, superb. And paint me jealous that you've achieved that level of mastery after so short a time and so few figures. Took me much longer and with many more embarassing figures I'd not let anyone see before I got near where you are now.