Chosen One Seren is the final boss of Cernium and the first boss of Continental Grandis, available for players above level 265.
Seren is a Level 275 boss and the final boss of Cernium, where she is being controlled by Gerand Darmoor and uses the sun god Mitra's powers to attack the player. While not introduced as a fightable boss during GLORY's storyline, she makes her first appearance as a fightable boss in the NEO update. As the first boss of Continental Grandis, a minimum of 150 Authentic Power is needed to deal normal damage in Phase 1 of the battle, and 200 Authentic Power is needed to deal normal damage in Phase 2. You must be in a party of 1-6 people in order to fight her, and each player has a Death Count of 5; if all players reach 0 lives, then the battle will end and everyone will be kicked out. The battle has a time limit of 30 minutes, and the players have a cooldown of 10 seconds on potions.
The battle consists of 2 phases and she can change forms during phase 2.
Currently, she can be only fought on Hard mode, and Hard Seren is considered to be one of the strongest bosses in the game, being at the same tier as the Black Mage.
- Gauge: Each player has a sun-shaped gauge during the fight. Each attack by Seren that hits the player increases the gauge. When the gauge is full, the player is stunned for 8 seconds, preventing them from moving, attacking, or healing themselves. The effects can be negated with skills such as Zero's Chrono Break or Battle Mage's Blue Aura.
- Meteors: Sun-like meteors will fall from the sky, dealing 15% HP damage and inflicting Blind to reduce your accuracy.
- Holy Pillars: Pillars of light rise from the floor, in a similar manner to the pillars of light used by Darknell. These deal 40% HP damage and increases the curse gauge. Note that binding Seren will not cause these attacks to stop.
- Rush: Seren rushes forward to attack the player, in a similar manner to Damien in phase 2. This attack cannot be avoided by ducking below it. It's a super knockback attack that deals 30% HP damage and increases the curse gauge.
- Impale: Seren stabs the player with her sword, dealing 15% HP damage and increasing the curse gauge.
- Lasers: Seren will summon diagonal lasers around her, which will cover the map in a similar manner to Lotus in phase 1 except they will behave like Lucid's and will disappear after a couple of seconds. Each laser deals 50% HP damage.
- Sword Aura Wave: Seren waves her sword and launches an aura wave, which travels across the map, in a similar manner to Warrior's Weapon Aura skill except that it's much slower and has a larger hitbox. While you can dodge the attack by ducking, you'll probably get hit by her other attacks because of the slow movement of the aura. If you get hit by the attack, it will deal 20% HP damage, stun you, and increases the curse gauge. If you're still in the aura's range, you'll get attacked by it continuously. Can cost many lives if you're not careful.
After Phase 1 is defeated, the players will be transported to the Barrier Between Worlds map, where Seren has finally awakened the powers of the Sun God. During this phase, Seren can change between 4 forms, depending on the duration of the fight shown in the gauge.
- Gauge: The gauge is upgraded by having clock-like parts that progresses over time, in addition to the curse meter from phase 1. The gauge is divided into 4 parts: yellow (representing noon), red (representing sunset), dark blue (representing midnight) and light blue (representing dawn). The parts are not even, and the midnight part is the shortest one. Whenever a player's curse gauge is filled, in addition to the negative effect shown in Phase 1, the midnight part becomes smaller. When the midnight part disappears entirely due to players constantly getting cursed, the entire party will fail regardless of each player's death count.
- Ray of Light: Near the end of each part, Seren will prepare an ultimate attack before she transforms. A yellow flame will appear at the top of the screen and shortly after light rays will descend from the sky, in a similar manner to Black Mage's ultimate attack in Phase 4. If you get hit by one of the rays, you will take 1000% HP damage and increase your curse gauge. You can avoid the attack by ducking below the rays or simply by using invincibility skills (if possible). Afterwards, she will take on the next form, with the background and BGM changing accordingly.
- Sun Rays: two sun-like spotlights will appear at the top of the map, firing sun rays that appear diagonally for a couple of seconds. Each sun ray causes continuous 10% HP damage, limits your visibility, and increases the curse gauge. Note that the attack will still appear even if Seren is bound.
- Mitra's Flames: A circle-shaped spot will appear on the map for a short warning duration and explode, dealing 35% HP damage and inflicting Blind to reduce your accuracy.
- Rush: Similar to Phase 1 except that the attack is much faster, deals 35% HP damage, and also inflicts Blind.
- Impale: Similar to Phase 1 except that it deals 20% HP damage.
- Laser: Seren fires a laser in front of her. The laser deals 35% HP damage and stuns the player. You can dodge the attack by ducking below it.
- Diagonal Lasers: Similar to Phase 1 except that the cast time is much faster and each laser's hitbox is wider.
At this form, Seren's attacks will be fire-oriented due to harnessing Spisa's powers, and therefore they will cause much more damage and some of them will apply Damage-over-Time.
- Flamberge - Seren will continuously summon large light rays on the floor, which will appear for 1-2 seconds as a warning period, and then will raise flame swords from the floor towards unlucky players who get caught by them, dealing 90% HP damage. Note that the swords will appear even if she is bound.
- Firewall - Seren will create two fire walls near the edges of the map in order to limit the players, making them more vulnerable to attacks, similar to Will's spiderwebs in Phase 2. Getting hit by each wall will cause 50% HP damage, as well as inflicting damage over time, which will appear above the player as a fiery orb.
- Fire Slash - Seren will swing her sword forward in 3 different poses. She can swing her sword, or stab you, in a similar manner to her regular stab except that its range is much wider. She can do multiple slashes in a row and if that happens, she will keep slashing even she's bound. Each slash causes 200% HP damage, and only the stab-like attack can be avoided by ducking below it.
- Flames of Spisa: Seren will drop a series of meteors, which will descend vertically from the sky into the field.
- Rush: Similar to Noon form except that it deals 50% HP damage.
- Impale: Similar to Noon form except that it deals 35% HP damage.
The duration of this form is the shortest but also it's the most important part, as it can decrease if a player fills his curse gauge. If it disappears completely, the entire party will be kicked out. Therefore, it's advised to avoid getting cursed as much as possible to prevent this from happening. Attacks in this phase will NOT cause the curse gauge to increase, so use it to your advantage.
It is considered the ideal form for players to deal burst damage to her, but the players needs to avoid getting hit by some of her attacks as they can inflict abnormal status effects and interfere their burst.
- Light Sparks - Small beams of light appear in several places on the map. Deals 15% HP damage and seals off your skills for a short period.
- Shockwave - Seren creates a shockwave to push surrounding players away. Deals 20% HP damage and reverse your controls.
- Rush: Similar to her other forms except that it deals 15% HP damage.
- Impale: Similar to her other forms except that it deals 10% HP damage.
In this form, Seren will harness Nerota's healing powers and therefore most of her skills will be defensive, focused on healing herself while using summons to protect herself.
- Energy of Dawn - Upon transforming, she will cover herself with a shield, represented by a white HP gauge that will cover 10% of her HP bar and will increase slightly as time goes. You cannot deplete that shield, and upon transforming back into her Noon form, she will heal herself with the amount of HP gained with the gauge.
- Nerota's Incarnation - Seren will summon the deer-looking physical incarnation of Nerota to chase the player. It cannot be killed, and getting rammed by it will cause 10% HP damage with a super knockback effect.
- Nerota's Power - Blue spheres will constantly spawn to pursue the player. When the player gets close to the sphere, it self-destructs, causing 25% HP damage and seals your skills.
- Azor's Descent - Seren will constantly summon swords that will fall towards the field vertically from the sky. Deals 25% HP damage and stuns the player.
- Traps - Seren will set traps over the field that behave in a similar manner to field mines. When a player steps over a trap, it explodes, causing 35% HP damage.
- Rush: Similar to her other forms except that it deals 30% HP damage and slows the player.
- Impale: Similar to her other forms except that it deals 15% HP damage and slows the player.
- This boss is at the same tier as the Black Mage (5 gold stars). However, it is a weekly boss while Black Mage is a monthly boss.
- Seren's forms at Phase 2 are all embodiments of Mitra and her lesser forms, Spisa and Nerota.
- This is the first boss to exceed the 300% PDR limit, as she has 380% PDR. However, it's not the first monster to have over 300% PDR, as the Red-eyed Gargoyle's Hidden Nightmare Clocktower in Lachelein had 930% PDR; the map along with those monsters were removed in Beyond / Override patch.
- In KMST, Some of her forms sported a whopping amount of 500% PDR while some had 300%. However this was changed in live version so all of her forms now have 380% PDR.
- This is the first boss that have additional failure conditions rather than running out of time or lives.
- This is the second boss that is actually an ally to the player. The first was Cygnus, who too became corrupted in the fabricated alternative timeline.