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. It is unknown who built Costlemark, but judging its arcane technology, it may have been part of the ancient civilization of Solheim.
Retrieving the Royal ArmEdit
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, and each panel must be completed in order. At the end of the dungeon, the party fights the Jabberwock that, upon its defeat, will drop the Sword of the Tall, one of the Royal Arms.
A Treasure Beyond MeasureEdit
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 CostlemarkEdit
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.