Monarch is a tier 15 cruiser used by the Fringe Systems Resistance.
One of the most dangerous enemy ships in its tier, you should be appropriately prepared to deal with this nigh-flawless rammer before engaging it. Fixed ions will have a hard time with this ship, so those using them may want to avoid fighting this ship entirely. Ships relying on missiles will also have a hard time due to Monarch's heavy usage of point defense. The best weapons to use against Monarch, then, are nukes and deck cannons. Ensure that your ship is either very strong or very fast, as Monarch can move very quickly and uses rammer AI. Don't rely on shields heavily - Monarch's eight disruptors will make quick work of them.
When fighting Monarch, target its reactors - it'll be easier to destroy its reactors than pick off every deck cannon one at a time. Once Monarch loses a reactor, you should be able to retreat out of range of its deckguns and then destroy the other one. While you can orbit Monarch, it turns very quickly, making this hard to pull off successfully. Flanking Monarch, however, is extremely effective as its backside is totally unprotected - sniping Monarch's control rooms is a viable option here.
If Monarch shows up in combination with other enemies, it is best to prioritize Monarch unless its allies are significantly larger or more offensive - such as nuke-armed Imperium cruisers. In particular, Monarch's point defense may interfere when you attempt to kill Monarch's allies.
