The wards protect; they ensure that naught of the evil infesting that cruel arboreal labyrinth can penetrate the walls of the old keep. Yet, reproducing them has proven unusually problematic, even for the most gifted scholars who dare venture into this reviled place.
Their patterns are complex, and the fine grain of the ashen stone used for the walls allows a great deal of detail to be inscribed. The first attempts were made upon parchment, these failed utterly as they elicited no effect what-so-ever. Masons came, carving the runes into stones bought through the portals, again these inert pictograms offered no protection, not did they when carved into wood or even crystal.
Then came the idea of prying loose a stone from the wall and inscribing upon that one of the, assumed, protective runes. No sooner was the rune completed when a baleful glow came to the rune, and our engraver fell dead in an instant, though not before screaming in such a heart rending way as to wake the few who find sleep in this place. The rune functioned well for all of three days before failing, a tiny flaw introduced as the engraver dropped her chisel proving to be its end.
Within the walls of the keep there are, at current count, thousands of runes carved therein. Such a terrible price to pay for an empty sanctuary that was, ultimately, empty.