Dark Iron pegs

These kinds of metal and bone pegs are driven through the limbs of some sci-fi and fantasy creatures, particularly the Hive from Bungie's Destiny universe as well as some assorted undead from the Legend of Zelda setting if I recall correctly.

There isn't any lore I've seen on the nature of these objects, but I would guess they serve as some kind of token of strength or the resilience of the bearer to pain. Its a bit grim, but for your miniature villains it might be their cup of tea.

They might do nicely as fantasy fenceposts or pitons as well.