These warships were commonly used by the Annwyn Empire for coastal protection, commerce raiding, and often pirate hunting. Frigates are a robust vessel, designed to be fast, shallow draft, and heavily armed.
They came in various sizes from the smallest 6th rate (like the HMS Lady Jezebel) to the progressively larger 5th and 4th rates.
Pirates were very rarely able to stand up to the might of even a 6th Rate ship however. Similarity any Pirate who could capture one and adequately crew it (they required up to 300 crewman to fight at their full capacity) bevame a serious threat.
The The Thousand Isles shipwrights currently do not possess the skill to build a ship so large and fast, so these ships are mostly legendary artifacts left over from the old imperial days. The Pirate captain Rose however has been experimenting with recreating the old designs, with some degree of success. Though her ship the The Wild Rose is smaller, lighter and less heavily armed then even a traditional 6th rate of the Annwyn Empire it is still a marked advance from other similarity sized ships on the seas.