Game-breaking artifact of paired gate pieces, surrendered by Carl as leverage and promised back on the ninth floor.
The gate pieces sat on Orren's desk under Administrative Hold during the interrogation, and Quasar revealed the trap: had Carl picked the artifact up while the hold was active, the item would simply have been deleted. Nobody in the Syndicate wants the game broken, but they are not allowed to take the artifact, and Carl's sponsorship and entertainment value offset the damage he might cause — the same calculus that surrounded Remex the Grand — so they negotiated instead.
Carl refused to sell, demanding collateral in the human fashion. The bargain: he temporarily gives up the gate and receives a mercenary upgrade with four bodyguards, Bomo, Sledge, Clay-ton and Very Sullen, two of them carrying Teleport to Stairwell and Zerzura to replicate the gate's abilities. Orren promised its return on the ninth floor, apparently because the corporations like the idea of Carl sowing chaos during Faction Wars — or, as Princess Donut suspects, because they expect him to die first.
A set of gate pieces small enough to sit on a desktop, last seen being cleared away by Orren.
The bargaining chip at the center of Carl's dispute with the Syndicate.
Also appears in books you've already read — spoiler-safe to their endings: