Elemental Ring

The people of Eberron use the elemental ring. It's a bound fire elemental that provides thrust in the ring, and by necessity, it's a colossal fire elemental that does the job. The fuel cost is that there is none, and the thrust output is virtually unlimited. The bound elemental is in a khyber shard that is colossal in size. The ships of Eberron are made of soar wood and live wood and are built to hold an atmosphere.