Prerequisites

The map to the Seaside Ruins will appear in Initium’s shop after you first visit the Boiling Sea, and will sell for 2,000 St. There’s very little reason to buy it, though, as you can reach the Ruins via Boiling Sea’s second map. It’s not a long walk, so save your money. 

Seaside Ruins - Tectonic Forum - Enemies
  • Death's Reaper
  • Lizardman Sentry
  • Mako Scout
  • Rockskin Brute
  • Spriggan Raider
  • Stickbug Sentinel
  • Stickbug Zealot
Well doesn't this look pleasant. If you've been following this guide you'll only run into a few new enemies in the Tectonic Forum:
  • Rockskin Brutes. Big, nasty, tough, hard-hitting enemies. They tend to take the heat on the front lines, and should be a top priority for killing. Make sure somebody’s on the defense for your whole team when a Brute is on the other side.
  • Deepsea Prowlers. They’re essentially watery versions of Stickbug Sentinels, and may use water charms on occasion. Otherwise they just hit hard.
  • Death’s Reapers. Reapers can use status attacks and debuffs to annoy your party. In particular, it can Poison your characters one-by-one. Death's Reapers occasionally use their sickles to do a lot of damage to one character, making them the prime target when one appears. (Which isn't too often.)
This area is as straightforward as they come. To the east and west are dead ends, so you might as well go straight north. You may find Sparkles in the next clearing, and past that are stairs leading down one level.


Seaside Ruins - Seaside Ruins 1F - Enemies
  • Death's Reaper
  • Heroic Prowler
  • Lizardman Sentry
  • Mako Scout
  • Mako Sun-Brother
  • Rockskin Brute
  • Spriggan Raider
  • Stickbug Sentinel
  • Stickbug Zealot
More ruins. There's one new enemy type you'll run in down here:
  • Heroic Prowlers. These more-advanced Prowler types draw away Water elements on a regular basis, restoring the enemy party's HP. Get rid of them promptly to avoid this.
There’s an intersection dead ahead. Start by taking a left, as straight ahead and to the right are both dead ends. The lower room down this hall has an ancient device, and the upper hall has another such device, slightly different in color. Near the second ancient device you'll find some stairs.

Once you can manipulate Fire elementals you can activate the ancient machine near the northwestern stairs on this level. This opens paths to the east and the west. The eastern path leads to the second floor, which we'll discuss in the next section of the guide, while the western path leads to a singing stone. The Whispering Shard you receive teaches Flare.


Seaside Ruins - Seaside Ruins B1 - Enemies

The path splits here, but the lower path leads to an ancient device you can’t activate and a loop that leads east anyway. If you take a left at the southern intersection you can find an ancient device for Wind-elementals, and beside it is another potential Sparkle.

To the northeast you'll find dirt floors, lava, and a second ancient device. There are stairs in the east leading to an exit, a third ancient device to the west of the stairs, and a bit more area to explore to the south. You can’t see much here right now, though, so unless you’re going for completion, take a right and go down the stairs.

As with the first floor, you can use the Singing Shard on the second and third ancient devices down here to bring in Fire elementals and open more paths, specifically the southwest section of the map. In the far southwest corner is a singing stone that will give you a Whispering Shard that teaches the Firebolt charm. If you also activated the Wind-based ancient machine near the stairs to the first floor you'll also find a teleporter in this area that'll shunt you to the northwest corner of the map, where you may find a Chest.


Seaside Ruins - Seaside Ruins B2 - Enemies

This place looks less hospitable. Check behind the stairs at the entrance for a potential Chest. You’ll find another possible Chest to the northwest, on the edge of a ledge. Watch out for superheated venting as you walk through here, or it'll inflict damage.

South of this second chest is a singing stone. This is not your ordinary stone, however, and it will grant you the Singing Shard of Fire. With this you can summon Fire elementals to your cause, and, by extension, use Fire charms via Fire Contract. You can immediately use it to activate the nearby ancient device, granting you a significant Fire boost in the area. Fire elementals increase your attack power when they’re on your side of a fight.

Continue west, down the ramp behind the nearest ancient device. There’s a potential Sparkle up a ramp to the northwest, and in the southwest you’ll find another ancient device. Activating it will bring Water elementals into the area. It will also open lava-coated pathways to your right and left. The left path leads to a yellow pedestal which will net you a Mason’s Chopper, as well as a cave leading to the map Final Depths. The right path also leads to Final Depths.