Manbearcat
Legend
Yes. That you don't see a way is somewhat telling.
The ruby is cursed. The ruby belongs to a powerful entity who now declares enmity. The ruby.... so many ways to make finding exactly what the player wanted into something that the character suffers for.
I agree.
The GM's primary role in TTRPGing (outside of a few instances) is (a) to know what adversity is relevant to this particular play and (b) bring that adversity to bear against the PCs in the imagined space in the most interesting/compelling/challenging/provocative (and these will be contingent upon the game) way possible.
Above I mentioned a Dogs play excerpt. The adversity I played was the intense shared longing through letters received on the road, provoking the PC toward finding out duty and discipline or desperate distraction?
In a D&D game featuring Fail Forward like 4e, in the fiction, the temple raider PC successfully pulls an Indiana Jones swap of the ruby for the bag of sand...except mechanically, the Skill Challenge was brought to close on that last check with a failed Thievery. The PC has the ruby...but the bag of sand had a rip in it from a narrow escape from a prior trap...now the sand is emptying to the floor and the trap has triggered a temple collapse (and a Healing Surge loss or 1/4 HP).
Now we have a new scene (a new Skill Challenge) that features a mad dash through the collapsing temple to the surface.
That fails (mechanically) right before they reach the surface. However, the complex doesn't collapse on the PC. The ruby is tied to a sleeping primordial. Taking it beyond the seal awakens the primordial, triggering earthquakes and devastation in the area (and eventually, down the line, the primordial itself). Further, the secret order that has sworn generations of oaths to protect the seal confronts the PCs on the crumbling stone balcony outside of the complex, overlooking a terrible fall. Boulders are falling on the balcony from the ridge above them. Lava geyser are erupting in cracks. And the PCs are all well down on Healing Surges from the two failed SCs and possibly going into the fight Bloodied.
Whatever the game's adversity is supposed to be is what you play as GM.
Just bring it.
Relentlessly.