Will learned a great deal from Ranrok's memories, but the most important part concerned Ancient Magic:
Ranrok's ancestor Bragbor was a highly skilled Goblin craftsman. He had built Repositories for five powerful Wizards to seal away potent Magic.
Those five Grand Wizards were Percival Rackham, Charles Rookwood, Niamh Fitzgerald, San Bakar, and their student Isidora Morgana.
The Repositories of those five Grand Wizards held powerful Ancient Magic. Bragbor had recorded this in his diary, but for a long time, no one had found it.
Then Ranrok and his younger brother Rohdgok found their ancestor Bragbor's incomplete diary and learned most of the story.
Ranrok began gathering those powers. To that end, he contacted Charles Rookwood's descendant Victor Rookwood and gained access to Rookwood Castle to dig and search.
And he really did find the Rookwood family's Vault. He stole some of its power, and even the Bracers on his arms were imbued with Ancient Magic stolen from it.
That was one reason Will was excited: his Time Travel had been worthwhile. What he wanted was close now.
So far, though, the Rookwood family's Repository was the only one Ranrok could locate. He knew nothing of the others and had sent Goblins under his command to search everywhere.
He was even building an enormous drill to make excavating the Vault easier.
He had attacked DePty and Professor Fig for the key they carried.
Will had little interest in Ranrok's personal memories. He searched through them briefly and found the reason Ranrok hated Wizards:
The Wizarding World was partly to blame. It had never treated Goblins well. Few Wizards took them seriously, and most looked down on them as little more than Fantastic Beasts with slightly more intelligence.
After being bullied and beaten by Wizards like that, Ranrok's outlook had grown even