For a long time all we had in light were the early ones before metal + troll.
They added fenris later, obviously mistlands later, and swamp's wood armor came later as well (as did the monster that drops the bits).
Its either an oversight, not done yet, or maybe never will be but if I had to guess its a TBD alongside a (maybe?? hopefully??) dungeon in the plains (also missing).

This is pure speculation, though. No mention of it to date that I know of.