Human: Generate for a magical scene inside a tunnel cavern with a massive wooden arch and mithril straps. Assistant: 
A massive, wooden arch has been erected in the tunnel here, its limbs and supports covering a ten-foot span of the irregular ceiling. Formed from stout felwood timber and banded with thick mithril straps, the arch appears to be quite sturdy. Minute, vein-like cracks in the stone ceiling and walls may have initiated the need for its construction in this area.