It may be involved in an upcoming update, or its development and release may have been cancelled entirely.
The life rune was a rune developed for use in RuneScape Classic, but which was never implemented into the game. It was intended to be a counterpart to the death rune for use in early Summoning, also called Necromancy, which at the time was intended to be part of Magic, but was never released in RuneScape Classic due to the limits of the game engine. Before the announcement of Summoning, the life rune was asked about by a player, who accurately described it, in the June 2007 Postbag from the Hedge. However, the response given by Historian Minas implied that the player had only heard false rumours. In a Development Diary in November 2007 Jagex explained the origin of life runes:
We actually made the life rune for Classic, but didn't release it. Some players discovered its existence, but there was no way to actually get it.