Take in mind I'm not talking about the Shanks and Servitor that are hanging around on the right at the very beginning. A purple cloaked Captain and two (or three?) Dregs drop in from a Fallen Dropship that is triggered by stepping on a far platform to the left of where the floating platform steps appear at the beginning of the Inverted Spire strike. Anyone else see them/fight them? There's a trigger point on the tip of the high platform past (and sort of behind) the milk water fall that is seen at the far left of where you would begin jumping onto the floating platforms. If you step on this hidden trigger, the dropship appears instantly where you just fought the Vex at the "entrance" of the floating steps that take you to the next section of the strike. You can defeat them and go back to that same trigger point to call them in over and over again if you feel like beating down some Fallen instead of Vex and Cabal.