Adamantine

Hard light drawing from an infinite power source. Absolutely does not bend or break no matter the force applied onto it.
There is a very limited amount of adamantine left in the world, a lot of it actually taking the form of tiny jigsaw-like shards.
Adamantine shards are essentially tiny interlocking pieces, which can be individually manipulated to fit together in order to form a larger object. Due to the perfectly inflexible nature of adamatine, there must be some sort of non-adamantine locking 'keystone' mechanism for all forces to end up directed to, or there will always be a way for the fragments to slide out of place.
As a result, man-made adamantine structures aren't truly indestructible. When their keystone is destroyed, the entire thing tends to shatter back into shards. Most pieces have multiple keystones in order to make design easier, although this introduces more weak points which can result in parts of the piece breaking.
With the revelation that hard light is the shadow of the soul imposing itself onto the world, adamantine takes on a slightly different tone. Isn't it essentially the shadow left by dead or vacant gods?