Oooh, some cool theories here! With regards to the potential of a 4th shard, Taravodium ponders the other shards in I-4: The Wrong Lesson: “He instead was most curious about the fact that two of the Shards appeared to be missing, completely vanished from interacting with the others. Hidden. One he understood with some effort. But Valor—where had Valor gone, and how did she hide from even his eyes?”. We also have some discussion of the other shards from Tanavast/Honor's perspective—for instance, chapter 115: Binding gives us: “WE COULD SENSE EACH OTHER. ALL EXCEPT A FEW—LIKE EURIDRIUS, HOLDER OF REASON—WHO HAD VANISHED. OR LIKE AMBITION, WHO HAD BEEN DESTROYED”, as well as “I MADE ONE FINAL ATTEMPT AT LOCATING VALOR, THE GREAT DRAGON GOD MEDELANTORIUS—AS SHE WAS A WARRIOR WHO WOULD SURELY JOIN ME. MEDELANTORIUS WAS NOT TO BE FOUND, UNFORTUNATELY”. Granted, these chapters are 7000 years apart, so things might have changed, but it seems the suggestion is that Reason might be the shard that took Taravodium some effort to understand?