Infinity Circuit

An infinity circuit is a psychic network contained in the wraithbone skeleton of a craftworld. They transmit psychic energy throughout the ship to power on-board devices, and since the fall of the Eldar, they also serve as artificial afterlives for Eldar souls.

When Eldar die, their souls are trapped by the spirit stones that they wear. These spirit stones are then placed in contact with the core of their craftworld's wraithbone skeleton, which draws the soul out and into the network. The soul's energy is added to the wraithbone's own, while its "personality" gets to finally take a rest, being safe from Slaanesh forever (as long as the integrity of the circuit itself is maintained -- that's what the craftworld's guardians and other armed forces are for).

Infinity circuits can also be sources of soldiers. If the need is truly dire, Spiritseers can guide souls out of the infinity circuit and back into their spirit stones, which can then be placed into wraithbone constructs like wraithguard, wraithlords, wraithseers, and even tanks to fight for the craftworld once again. Eldar don't like doing this, because they prefer to leave their ancestors in peace, but sometimes it just has to be done. Craftworld Iyanden probably use the most such "ghost warriors" after sustaining terrible losses against Hive Fleet Kraken; they put themselves through so much angst over it that the Dark Eldar found it funny.