The Black Disciple upgrade can be purchased at the Black Hand Nod subfaction's Secret Shrine building for 1000 credits. This is a good investment of resources even in the early game, which significantly bolsters the anti-infantry and anti-structure capabilities of the Black Hand's most basic infantry squads, and also allows them the ability to clear out buildings. In addition, it offers some extra firepower against enemy vehicles, particularly if the more expensive Purifying Flame upgrade is in effect.