[SolemnGolem]

Inspired by the responses to this thread, I went back to the Low Tech books and found a good number of weapons and materials that a non-metalworking society could have.

I was less confident about whether or not to make stone off limits, which I think would still be quite a useful building and weaponry material (obsidian spear points and arrowheads, for example). I've been toying with a limitation that "all materials they use must once have been alive" to fit in with their "one with Nature" theme. This leaves open the possibility of shells, teeth/fangs, and sharpened bones and so forth for weaponry, but closes off most rocks and all metals. (As a side note, if carved shells are important as a source of arrowheads, then it could give rise to interesting geographic priorities or sacred sites for the elves. A prehistoric riverbed-turned-hillside in their forest, which also happens to provide the only source of ancient shells, could become a Place To Be Highly Defended if they have no other source of useable arrowheads.

Armor could be fashioned from animal skins and shaped wood (magically if need be) and weapons could maintain a decent forest deterrent with bolas, slings, spears, bow and arrow, caltrops, and potentially even grenades with contents such as burning pitch, sleeping powder, madness spores, and the like.

Vehicles such as wagons, chariots, and carts would not be used, not least owing to their problematic material manufacture, but also perhaps aesthetically being non-pleasing to the elf who prefers to "feel the life of Nature by their skin". Mounted transportation could still be done naturally, if elves are deemed to be able to ride woodland animals like deer - similar to Prince Ashitaka riding a red elk in Princess Mononoke.

Magery or other powers could be limited by the Nature limitation, so they may even deactivate altogether if the elves venture into higher-TL areas. Combined with their limited options for vehicles, this could make the elves a permanent sylvan guerrilla race, quite willing to raze human (or other) higher-TL settlements, but unwilling to take them over for their own.

Obviously, my vision for elves in such a campaign would completely avert certain fantasy tropes ("blond pointy eared skinny nobles wearing platemail, holding their elegant steel rapiers amidst the soaring marble spires of Palace Clichéfael" etc.) but I think it's a good basis for a nature vs. civilization narrative contrast.