Root Lurker is the boss of the Mandolin Church Catacombs in the World of Eternal Sonata. It appears before the party as they reach the depths of the area, investigating the odd noises that the citizens of Ritardando heard underneath the Mandolin Church.
- Beat: "There it is. It looks like that's our 'ghost.'"
- Viola: "So this is what's been living down here."
- Salsa: "What? That's it? If it's not a ghost, then it's no problem at all."
- — The party is pleased to discover the "ghost" of the church is just a monster.
When Frederic, Allegretto and Beat take a tour of Ritardando following their reunion in Chapter 5 - Nocturne, they discover a commotion outside of the Mandolin Church. A large group has gathered, trying to figure out what to do about some strange noises heard coming from underneath the church. The church's basement was used as a shelter against pirate attacks in the distant past, but now abandoned, it's apparently become a breeding ground for monsters, and possibly ghosts. In the commotion, the lady that owns the bakery spots Allegretto & Beat and recognizes them as the two children who have been stealing for her. Though they protest that they had a good reason, the citizens of the town decide that they should go investigate the source of the noises as penance for their previous bad behavior. Frederic agrees to help.
As they make their way into the church, the doors of the church open and March, Salsa and Viola appear. They explain that they had just arrived in Ritardando, spotted the commotion, and saw Allegretto, Beat and Frederic entering the church. Just then, Allegretto excuses himself from the proceedings, saying that he's going to go fetch Polka from Tenuto Village and that with so many talented people, they don't need his help. Beat is shocked that he would just abandon them, but Viola suggests that he's afraid of ghosts and Allegretto gleefully seizes on this excuse. The party, sans Allegretto, makes their way through the church catacombs and eventually reaches the depths, where they discover that the "ghost" is actually just a fierce monster.
The Root Lurker's normal attack is either a butting or popping attack on all characters grouped close together. It tends to rely mostly on a roster of powerful Special Attacks. Its most dangerous attack is Trip To Pain, a piercing attack that charges through characters in a line with a chance of knockdown. It may then follow this up with a normal physical attack or another Special on a character from behind if it has time before its turn runs out. Bo-Peep is a popping attack on a single character that carries a chance of causing Passive status. Roar is a magical attack from a slight distance that hits all characters in range. Finally, it has a dangerous Deep Bite attack that deals three hits of damage on a single target.
The Root Lurker possesses some fairly powerful attacks, but the party has some new advantages with the ability to use a Harmony Chain following a powered-up Special Attack and also the ability to Counterattack. Equip the Leather Guard to everyone in the party for a strong chance of protecting against the Passive status that can be inflicted by the boss's Bo-Peep. The party choice is really up to the player, but Viola can be quite helpful for both her healing and marking the boss for damage with Hawk Eye, and Beat can take Photos if Gold is needed.
The Trip to Pain attack is by far the most dangerous attack, but it is also easy to Guard against and is also reasonably easy to Counterattack if the option is offered. Counterattack can definitely be a lot of help in this fight if used, as it will bring the boss's turn to an immediate end, allowing the party a free shot at it, plus a bit of additional time to use normal attacks to build up Echoes. Most of the other attacks are also fairly easy to Guard against, but be ready to have Viola or Frederic heal if needed, or just use items. If Salsa is in the party, she can increase the power of Special Attacks with Shadow Silhouette and if March is used, she can protect the party with Aurora Curtain and build up a lot of Echoes with Super Nova. March can also inflict Stop with Full Moon Bind, effectively cutting the number of attacks it can do during its turns (this is especially valuable during Encore Mode).
In Encore Mode, watch out, as some of its attacks can be a KO or near-KO in one strike if not Guarded against or Counterattacked and it will very often get two turns in a row. Bring in a Very Odd Chocolate to decrease its attack as well as a Sock Incense to decrease defense. Stock the remainder of the item set with Angel Trumpets and Goddess Bouquets and rely on Frederic and Viola for the remainder of the healing. It may also be worth including a Wormwood to poison the Root Lurker, though it will often resist it, and it really isn't necessary with the right strategy. The party should be above Level 30 to get sufficient turns against the boss.
- In the XBox 360 version, the player is rewarded with the Crimson Brooch in addition to the Herebra for defeating this boss. In the PlayStation 3 version, the party only gets the sword; the Crimson Brooch is a reward for playing Score Piece 11 with Conceited Choir in the Side Garden area of Baroque Castle. (In the Xbox 360 version, he gives an Odd Chocolate instead.)