This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Sileni (Greek)
In Greek mythology, Silenus was a companion and tutor to the wine god Dionysus. He is typically older than the satyrs of the Dionysian retinue (thiasos), and sometimes considerably older, in which case he may be referred to as a Papposilenus.
Silen and its plural sileni refer to the mythological figure as a type that is sometimes thought to be differentiated from a satyr by having the attributes of a horse rather than a goat, though usage of the two words is not consistent enough to permit a sharp distinction.