Krayzikk,

Welcome aboard! To answer your question, magicians are your typical Red or White mage. Elemental magic mostly. Historically the kings of Europe used them as another tool to keep the peasants in line and while I was planning to go into it in more detail later, the French Revolution was a response to King Louis overusing his magicians against the people. So there's some historical animosity there to add tension.

Aboard a ship, magicians usually keep the boilers running without coal, using only their magic (Though on a Man o War, there is usually a team of magicians working round the clock). 

Feel free to write up a CS and ask any other questions!