The rewards were nice and all but for now, that wasn't his priority...
Since he already passed the test, his advancement will now begin.
As if on cue, Cedric felt a strange sensation bubbling within him. He became alert and immediately sat down to brace for the impact.
Boom!
Cedric's body shook. A wave of pure unknown force slammed into him, causing him to groan uncomfortably. Nevertheless, it wasn't threatening. He hurriedly relaxed his body allowing it to absorb the foreign energy that was being transmitted to him.
While the list of requirements didn't include Demon Souls, it's under the premise that all system users know that every advancement needs it. A given fact, more or less.
For Cedric's Tier 3 Advancement, he needed a whopping 150,000 Purified Demon Souls. For others, this would've been impossible to get but since Cedric could collect them, this was no problem for him.