The Black-Stained Blade (A Riddle)

Fun, unexpected exercise for Brit Lit resulted in this little guy. We were assigned a poem of 10 lines or less abusing the tropes of traditional Anglo-Saxon verse. These include (for those interested) kennings, regular caesuras, abusive alliteration, negative understatements, boasting, riddles, and four stress lines without stanza among other things. Anyway... (Read aloud with an old english accent).

My rightmost thumb, tensing and taut Enwraps a pommel of forge-spun steel. Black cast it carves, dripping of blood And fields lay fallow, perpetually stained. Trophies of triumph strew the wall and the shelves; Leather skins and spines hang lining my hall. And in peacetime and war, I grasp hard the hilt. No tame touch falls from my man-made tool. Words of my weapon will last out the age And no slight name do I sign with its blade.

Hint: (You might recall I'm Seamus' spade).