The blog from Jagex gives a few details and updates on the new systems that'll eventually be coming to the game.

Inside one of its treasure-filled burials—which date to the fifth and sixth centuries C.E.—they have also unearthed a well-preserved sword ... all of its mysterious runes.

Dating to the fifth and sixth centuries C.E., the burials held a trove of grave goods—but the team was particularly impressed by the sword ... all of its mysterious runes.