Thanks to a life force that constantly depleted itself, Decay aged rapidly. To survive, he absorbed the bio-energy from organic matter, which caused him to revert to a staple younger state. But Decay made a significant – and ultimately deadly – miscalculation when he siphoned off the energy from a source far too powerful for him.
On the Acolytes' mission to Wundagore Mountain, Decay attempted to absorb the High Evolutionary's energy. But the power proved too great for him to handle and caused him to explode. This energy ended his life instead of extending it.
Matter Disintegration: Decay aged rapidly because his personal life-force was constantly depleting itself. He absorbed the cohesive bio-energy from organic matter to survive, replenishing his own energies while turning the organism to dust.