These type of ships are not very frequent since they are extremely expensive and complex to build.
The most wonderful thing of a Fireship is that it is one of the very few types of ships in Sheta that contains a Spirit Crystal. Consequently these means of transport are somehow equivalent to little Islands with some crystal granting great powers to the crew.
The fire magic is needed for two reasons: to bind the gem to machinery itself and to sustain it; for some unexplained reason, Spirit Crystals which are not bound to Islands tend to slowly fade. If they are not somehow replenish they might even crak and dissolve into nothingness.
The machinery needs to fullfill two main tasks: to contain the Crystal comfortably and to channel its power into a functioning steam engine. Earthsons are the only ones to have this technical knowledge.
After the alliance witht the half-elves, at least one or two fireships have been known to be enhanced with elven magic. It is not sure if this was done through Mathema or the Flow (or both), and even the results are still not widely known.