Grandmaster looked deeply conflicted. He pursed his lips, waging an internal battle, but ultimately shook his head. "If these humans gather all the Infinity Stones, who knows what crazy things they'll do? If they really destroy the universe, I probably won't escape either. Forget it."
"All right, I was only making a suggestion." Schiller gave a slight shrug, making it clear that he had no intention of forcing him, then continued, "But I am curious—which Infinity Stones do the Collector and you each have?"
"The Collector has the Space Stone, while I have the Power Stone. The Power Stone originally belonged to the Champion, but he lost a bet to me, so I'm holding it for him."
Schiller calculated silently: the Time Stone should be with Strange in the Central Universe; the Space Stone should now be in Doctor Strange's hands; the Power Stone was with Grandmaster; the Mind Stone was with Loki; the Reality Stone was set into Thor's crown. That meant only the Soul Stone remained unaccounted for.
Marvel had actually already gathered three Stones: the Time Stone, the Eye of Agamotto; the Mind Stone, Loki's scepter; and the Reality Stone, the God of Light King's crown. If Doctor Strange brought back the Space Stone he had taken from the Collector, that would make four. They would only need to find two more to complete the Infinity Stones.
Besides, Marvel had locals leading the way. Surely someone among them knew where the missing Soul Stone was. Even if they did not, finding it through the Sanctum Sanctorum would be relatively easy.
In other words, aside from the one in Grandmaster's possession, the rest might all have fallen into their hands. That made Grandmaster's Power Stone extremely important. Even if Schiller could not get it himself, he could not