The Shadow Triad is a group of three ninja-like Team Plasma subordinates that are only loyal to Ghetsis. They don't appear to have any feelings, which is evident at N's Castle when one of them says a bit about N's Playroom, and says that he doesn't feel anything at all when he goes in there.
They make one final appearance after the defeat of Team Plasma; when the player has access to the new areas of the Unova region, the trio will appear on the Marvelous Bridge near Nimbasa City and inform the player that Ghetsis has gone off to another region to rethink his plans. Before departing, they gift him/her with the Lustrous Orb, Adamant Orb and Griseous Orb - the three items that power up Palkia, Dialga and Giratina respectively. They explain they gave the player these items as it was their master's wish. They depart, wondering what to do as Ghetsis has relieved them of active duty under him after this task.