Costlemark Tower

Costlemark Tower is an optional dungeon in Final Fantasy XV located in the Fallgrove in southern Lucis. The player must defeat the boss at its end to acquire a royal arm. Entry into the dungeon is required to complete Dino's final sidequest, A Treasure Beyond Measure.

The dungeon's entrance is magically sealed and will only open at night.

Costlemark Tower is a labyrinth of underground ruins. Although remains of large structures remain above-ground, they are all but gone in present day, and what is left is the underground portion. Costlemark was once part of the ancient civilization of Solheim, but now lies in ruin along with its arcane technology.

Warp-striking at the area with the moving blocks can be glitchy. If the player clips through a wall and there is no platform beneath them, they will fall into the abyss before being teleported outside the dungeon entrance.

Retrieving the royal arm
Costlemark Tower is populated with powerful enemies and the quests associated with the location recommend that the party be at least Level 55. The dungeon is structured as a mostly linear descent into the underground. As the party approaches the end there is a large chamber dotted with floor panels. Each panel leads to a gauntlet of enemies situated in a randomized maze which will either lead to the end of the dungeon, or a large room underneath the previous chamber where the player will have to fight a Red Giant reinforced by many Flans; each subsequent visit to this room increases the difficulty of the fight, culminating in three Red Giants and a Nagarani.

Once the correct path is taken, an elevator takes the party to the end of the dungeon, where they fight the Jabberwock that, upon its defeat, will drop the Sword of the Tall.

A Treasure Beyond Measure
Dino sends the party to acquire ore at Costlemark Tower as his final request. The quest becomes available after completing "No Gain, No Gem". Dino asks for an Emerald Stone which is found deep at Costlemark Tower. Completing the quest yields 3,000 EXP and an Emerald Bracelet.

A Menace Sleeps In Costlemark
This optional sidequest, with a recommended level of 99, is one of eight quests given to the party by Ezma in Chapter 15. To start the quest one must complete the main game and collect the Royal Arms from the following dungeons: Costlemark Tower, Crestholm Channels, Balouve Mines, and the Daurell Caverns.

When the prerequisites are met, the sidequest will appear at the Meldacio Hunter HQ southeast of the Vesperpool. Once the party speaks with Ezma, she will hand over the Sealbreaker's Key which will grant access to the mysterious large doors found in the lowest sections of the dungeons and begin the overarching quest Menace Beneath Lucis. To begin the quest A Menace Sleeps in Costlemark, the party must enter Costlemark Tower and return to its lowest level, where a sealed door awaits.

Upon entering the sealed door, the party's map and the item menu will both become inactive for as long as they're inside. Similar to the other sealed dungeons, the party will follow a linear path battling room after room of progressively stronger foes with a reward present in the center of each chamber. Battles within the sealed door cannot be fled.

In the final room, a treasure awaits in its center. As Noctis approaches the item, the Bilröst will attack. After defeating the boss, the quest will end and Noctis will be able to collect the Dark Matter Bracelet.

Menace Dungeon
The second longest dungeon and easily the hardest. No items can be used once through the sealed door, if Noctis' health falls to 0 and the party can't help him out of danger, the player will have to start again from the last haven.

The party should be level 90+ before attempting, and could benefit from a more defensive build. The accessories Magitek Suit V2, Black Hood and Anklet of the Gods are good choices. The Grand Chamberlain for Ignis can be useful also but isn't reliable. Most enemies in the dungeon are weak to daggers and greatswords, but the "boss" enemies are weak to swords, so the Zwill Crossblades are a must-have, and either the Ultima Blade or Balmung can help when parrying.

Some other precautions can be taken before entering:
 * Stock up on magic with healcast, and enter the dungeon with full elemnts and healcast items for elemancy.
 * Take ingredients for recipes with the best buffs - Legendary Herb-Grilled Whopper is useful early on but when magic becomes vital - King's Stew and Kenny's Secret Recipe are among the best.
 * Have recovery skills in Ascension to try to keep the party alive longer. A lot of the harder battles will result in only Noctis being left alive.

Enemies

 * Gelatin
 * Galvanade
 * Thunder Bomb
 * Ereshkigal
 * Bussemand
 * Yojimbo
 * Red Giant
 * Flan
 * Nagarani
 * Garchimacera
 * Jabberwock (boss)


 * Havocfang
 * Hobgoblin
 * Mindflayer
 * Malboro
 * Iron Giant
 * Jormungang
 * Goblin
 * Braindrainer
 * Elder Coeurl
 * Uttu
 * Serpentess
 * Bilröst (Menace boss)