Mithril dragon, a dragon which spawns only if you (or possibly any creature on the level) is carrying over 75 aum of mithril in open inventory. It eats mithril items (and only mithril items, rather than being generally metallivorous).

Mithril items cannot be forged. It’s too good of a material to apply to arbitrary items, and there is lore which would back up it not being a material an amateur is capable of smithing.

Mithril body armor prevents the Tsurugi of Muaramasa from bisecting you (or a monster wearing it, for that matter).

The material of an object affects its ammo breakage chance. For instance, mithril arrows hardly ever break, whereas wood breaks a bit more often than normal iron.

It’s harder to force the lock on chests or large boxes made of metal, and increases the chance your weapon breaks. Additionally, the material of the weapon used to force the lock affects the result, if it’s used to pry rather than bash:

• Iron and metal behave as normal.
• Mithril is stronger than iron, and breaks less.
• Copper is slightly weaker than iron, and breaks a little more often.
• Softer metals, such as silver and gold, break less often but tend to bend. A “bent” weapon doesn’t actually become bent internally; it just loses a lot of enchantment.
• Wood is about as good as copper.
• Glass almost always breaks, and can break even if used to bash open a lock.

Crude (orcish) items should never generate with valuable metals (gold, silver, platinum, mithril) as their material.