World-Trees are covered by a layer of stone. Underneath this is their thick, lignin-infused flesh, and then another layer of stone.
They have enormous 'branches' and 'roots', which absorb matter from the void for growth and repair. It travels through their body in enormous tubes.
They are colossal in size, up to a million miles long. They can live for a billion years.
World-Trees often host much life. Aazep offspring live inside these structures.