Rassilon
From Jenny Everywhere Wiki
The Infinity Rassilons was a book by Percival Lankin pertaining to the Time Lords' place in the Multiverse, which notably elaborated on the nature of the Batrachian Casket. Jenny Nowhere once showed a worn copy of the book to one reality's First Doctor when revealing to him that his home dimension was not the “real” Third Universe. (PROSE: How To Steal Timeships & To Influence Time Lords)