Geralt still had a vast amount of Chaos power inside him. To the Four Gods, he was a battery with enormous capacity. The reason they thought of him as a battery, rather than believing their power had gone down the drain, was...
Before their power had been completely drained, the technique had deliberately left a line open. It gave the Four Gods the illusion that their money—well, their power—was still under their control, so they could safely keep investing power to corrupt Geralt until their own power gained the upper hand and turned him into a complete vessel.
And, as a bonus, a battery.
That power seemed to still belong to them, but that was only how it looked. In reality, their power had already been locked in place. They couldn't withdraw it at all.
In fact, if they tried to withdraw the power inside Geralt, they would find that, because of his unique nature as a transmigrator, the four forces inside him had formed a special ring-lock structure with him. To extract the power within, they would have to inject a huge amount of power in an instant—several times the total power currently inside Geralt—and completely break the ring-lock before they could get it out.
In other words, they had to put in more money before they could withdraw what they'd already invested.
Makes perfect sense, doesn't it? He was a transmigrator, after all. He had to be a little special!
If any of the gods really wanted to give it a try, the others wouldn't just sit back and watch. They would increase their energy injections, creating a stalemate. They'd have no chance to verify whether their suspicions were true.
After all, with so much energy being injected, there was no way they could extract it. By their