Abel wasn't sure what would happen, so he decided to place the three dark-golden crystal core pieces into the Horadric Cube first. When he did, though, the synthesize button became grey. This meant that he couldn't combine the pieces into a better piece. He would have to look for other ways to find himself the materials to create an advanced level rune.
While Abel had never used an advanced level rune for his research, he did have his fair share of experience when he was back at the Holy Continent. Any runes that were above #10 would require advanced-level ingredients. He knew that much. In other words, runes from #11 were supposed to be synthesized with lower-level runes.