Mederi works by retrieving the injured/nearly dead and patching them up, then letting them die painlessly (Because someone automated the system and now it's going overboard). On top of that, it has been noted as sitting on the same key line as a number of other death themed planets. I'm thinking the Warrens and the Leyland are connected, putting Tailgate in range of Mederis retrieval system once his spark started flaring up.