The mithril sword is a sword in Survival Beginnings.
The mithril sword is the strongest sword in the game, and the first item you should make with your mithril if you're an offensive player (although a pickaxe is recommended so you can mine more mithril later). It provides defense superior to any other, and will dispatch with ease anyone who stands in your way. It is the superior form of the steel sword.
Be careful because even with it you can still die and possibly lose it.