It takes the form of three probes which when fired at a planet split in the atmosphere burying themselves approximately 600 motras from one another. The planet then suffers from harsh magnetic shifts which destroy complex life forms not adequately protected.
The technology is not fully comprehended, that, combined with its power, lead to a very high value, and make it incredibly dangerous.
Though it was thought they had died, activation of the triangle had created some form of temporo-magnetic stasis which was reversed when John Crichton, Jool, and Chiana, recombined the probes, reviving the Eidelons and retrieving their monolithic temple. ("What Was Lost - Resurrection")