Shardminds in this world all have numbers assigned to them.
From Captain Brainbridge:
The abyss never belonged to the nine hells. In a great battle, in hell, a rift was opened – the breach – that ripped into the outside dimension, or as we would call it, chaos. That is how races like the dragonborn evolved, the great metamorphic genesis. The gods were able to seal it very quickly by creating a very powerful crystalline wall. Otherwise all the planes would have been destroyed. But in a later battle, the wall was cracked, and remains cracked. Legend has it that the fragments scattered throughout the planes, and became shardminds. Some people believe that when one shardmind dies, another shardmind is born with the same number. Other people believe that when shardminds die, they return to the wall.
Shardminds typically take one of three paths:
1. The path of the slayer – killing all shardminds with the idea that
2. Killing other shardminds to become powerful enough to repair the wall
3. The path of the scholar – researching to find a way to repair the wall
Shardminds seem to somehow retain abilities from past lives, but not memories. For instance, Ruby can speak abyssal somehow.