Instant cast right clicks (or procs) never use reagents. If this had a cast time on it, it would use a reagent to summon, but since it's instant, it doesn't.
No, seriously...it came from a chest/coffin in a cavern-themed Mistmoore Catacombs LDoN dungeon. Dropped for a group of all 65s. I watched Hae loot it to save it from rot (no monk in group).
Aye, I too got one of these out of a locked barrel (chest) in North Ro LDoN, Takish-Hiz. This was before they did a nerf on LDoN. I'm having to reflect back on memory here, but I think there was two big nerfs to LDoN. The first came within a few weeks of the expansion. The second came a few months after it's release. There was no longer at least one named NPC in every dungeon, and the quality of loot in the chests went down.