Coeurl is an enemy present in Etrian Odyssey Untold: The Millennium Girl. It is the main boss of Gladsheim AREA I, fought in a dark room alongside two Carmine Beaks. It can only be fought in the story mode.
This creature, vaguely resembling a large black panther, uses its agility and strength to great effect during fights. Being able to deliver lightning fast strikes and even put its prey to sleep, it is a great threat to the Highlander's party as they explore Gladsheim, searching for a terminal mentioned by Frederica.
It's main ability, is to turn nearly invisible in dark environments, forcing the party to avoid it as they search for a way to light the room the creature lives in. Only then they can fight Coeurl.
Very little information is given on Coeurl's origin. Acording to Simon, it was kept by Gladsheim's researchers for unknown reasons, until it escaped captivity and killed a large number of scientists. Afterwards, it was left free to roam the ruins to this day.
Once you first enter the room, you will be forced to fight Coeurl in the darkness. That means it will be invisible, and invulnerable to damage (it is possible to defeat it like this, but it takes a lot of time. Refer to the Trivia section for more information). You must run away from the fight, and reach the door in the northern side of the room. Coeurl will stop chasing you for a few steps, giving you enough time to reach it. There you can finally light the room.
Before fighting it, it's recommended that you kill the two Carmine Beaks flanking it. They'll quickly join the battle if you don't, and being FOEs, they can make the fight a lot harder. Should they join, however, you should still focus in killing the boss, as it's death will finish the battle regardless of any still-living enemy.
Coeurl itself is a quite difficult boss. It is faster than most party members, and hit for a lot of damage.
It's main attacks are Avidya Apostle and Dark Cradle. The first one hits the entire party for heavy damage, easily killing your weaker characters in a single hit. Leaving them in the back line and using Rear Guard with Raquna is recommended. Once it's health drops low enough, Coeurl will start using Dark Cradle, which has a medium chance on inflicting sleep on the whole party. This attack is extremely dangerous, and is often followed by Avidya Apostle, possibly wiping your entire party.
First of all, binding it's head and arms (blocks Dark Cradle and Avidya Apostle respectively) with Frederica's sniping skills is recommended, as it will greatly lower the boss' attack power, and, in head bind's case, lower it's resistance to elemental attacks. Arthur should focus on Ice attacks, the boss weakness, possibly alongside Analysis, boosting the damage dealt. The Highlander can both use Bloody Offense and Spear Assist, to improve the damage dealt. Simon's refresh (or a large stock of Therica Bs) is crucial to aid against the possible party-wide sleep, leveling it to level 5 is recommended. Salve can also aid against the large amount of damage dealt by Avidya Apostle.
- Avidya Apostle (Uses ???): Heavy damage to the entire party. Very dangerous and can easily kill weaker characters. Uses more frequently when hp is low.
- Dark Cradle (Uses ???): Inflicts sleep on the entire party. Often uses Avidya Apostle on the next turn. Only uses when hp is low.
- Nightmare (Uses ???): Heavy damage to a single character.
- Gloom Strike (Uses ???): Medium damage to a character row. Removes buffs.
- While the boss is immune to damage when the room is dark, you can still damage and kill it through poison. This method is extremely time consuming however, and should only be attempted if you seek a challenge.
- You can throw flash bombs while the room is dark to temporarily make the boss vulnerable to attack, the boss will become invisible again after the turn is over.