When you sleep, your soul briefly returns to the place where it was created/goes to when it dies, and seeks nourishment. Everybody's soul is created with a little link (or you could say a greater entity calls it back) to that place so that it can return easily, but upon death, the soul returns via that and annihilates the link as if returns.
Also, as an added thingy, you could say the entity supplying the link, or residue of the links themselves, (whichever) is the source of all arcane power.
The bronze Gladius Tyrvaard carries has been enchanted by the Spirits to be very heavy to any but the wielder. Tryvaard (or any others who use the blade) will find the sword light and easy to wield. Those on the receiving end receive a strike as if made by a much larger and heavier blade. For such purposes (damage, ease of parry, breaching armor), it strikes as if it were a two-handed sword of great size. The blade, being spirit-forged, is also extremely durable, well stronger then normal bronze.