From Destinypedia, the Destiny wiki
The Martyr's Retribution is a Legendary Grenade Launcher obtained from the Sundial during Season of Dawn. It is the first and only "Wave Frame" archetype Grenade Launcher in Destiny's history, and could also be acquired from umbral engrams. Wave Frame Grenade Launchers function by shooting out an explosive shell that detonates upon impact with the ground, releasing a "wave" of energy very similar to that of a Titan (class)'s Thermite grenade. Wave Frame launchers are designed to be pointed at the ground directly in front of where you want to deal damage and are highly effective at clearing waves of low-tier enemies very quickly, especially in activities such as The Reckoning.
"There seems to be no end to them. No matter how many I destroy, there are always more. An infinite, ceaselessly multiplying array of circuits and fluid. New units replace their ruined predecessors, forming out of sapphire transmat clouds. They want me dead. They won't stop until I meet my demise. They persist.
"For all their vast knowledge, they seem to have one blind spot. They should know by now, I also want them dead.
"And I won't stop either."
List of appearances