Panthalus

Panthalus is a capture, not a kill - it is the key that opens the World Tree. The fight is a 10-minute damage race against 353,220 HP, so the preparation matters more than the execution.

At a glance

How to open the Panthalus dungeon

Admin work, no difficulty to it. Speak to the Ancient Civilization Researcher on Deserted Islet to accept the quest - this marks all four whale skeletons on your map. Loot one Echobone from each:

• Marine — 124, -525 (on top of a skull, western waters)
• Silent — 356, -110 (in water atop bones, eastern side)
• Seafoam — -514, -549 (volcanic area, bring Heat Resist)
• Tidewind — -262, 485 (near Land of Absolute Zero, bring Cold gear)

Craft the Echoing Flute at any Workbench, a Primitive one is fine, then return to the Researcher and play it at the glowing shrine beside him. Panthalus spawns immediately, so arrive already geared and mounted.

Prepare your Pal

Every candidate below converts your attacks to Electric while you ride it, which is the whole point - your weapon does the damage, the Pal decides what element it lands as. What separates them is whether they keep you off the ground.

Take Beakon. Univolt has the strongest damage rider of the four - an attack boost plus 25-40% bonus Electric damage against Electric-weak targets, which Panthalus is - and it is the obvious pick on paper. But it is a ground mount, it cannot get you airborne, and this fight is won in the air. Helzephyr Lux flies and converts, so it is a straight substitute if you have no Beakon. Solmora Lux only swims, which leaves you at sea level in the path of the tidal waves; treat it as a last resort. Beakon also gains up to +25% move speed, scaling with how many Electric Pals you are carrying.

Fill the rest of the party with Electric Pals to feed that speed bonus - they contribute it just by sitting in the party, without ever being sent out:

• Rayhound - throughout the Desiccated Dunes, and an Alpha boss in Cavern of the Dunes.
• Dynamoff - Lv. 67 field boss southwest of the Sunreach Watchtower fast travel point.
• Grizzbolt - No. 1 Wildlife Sanctuary on the southern edge of the map, which needs a flying or swimming mount to reach. No overworld Alpha, so otherwise breed Mossanda with Rayhound.

Skip Orserk despite the stat line - it only spawns inside the World Tree, which is the thing this fight unlocks. Hatching one from a wild Huge Dragon Egg is the only way to field it beforehand, and that is not worth planning around.

Do not send out a separate attacking Pal. The Ring of Mercy covers you and your mount, not a deployed Pal, so anything fighting alongside you can punch through the last point of health and kill the capture. Ride your damage instead of deploying it.

Requirements

• All Tower Bosses cleared across Palpagos, Feybreak and Sunreach. This is the real gate, not character level.
• Ring of Mercy equipped. Caps your damage at 1 HP so the capture cannot be overkilled. See Notes - it does not cover everything.
• Ranged burst weapon. Rocket Launcher (Tech 65) is the pick for damage against the timer. Bring far more ammo than feels necessary.
• Ancient armour set - Ancient Helm, Armor and Shield (Tech 68-71), so level 71 or above.
• Basic Pal Spheres. The capture at 1 HP is guaranteed, so do not spend Legendary or Ultra spheres here.

Route

1. Equip the Ring of Mercy before you play the Flute. Do it then, not mid-fight.
2. Mount your Electric flyer and stay airborne for the whole fight - flying dodges most of the moveset, including the tracker bubbles and tidal waves.
3. Target the blue sigil on its forehead for weak-point damage. If the head will not line up, dump into the body rather than whiffing shots against the clock.
4. When a large AoE winds up, fly out over open water and return once it lands.
5. At 1 HP, throw any basic Pal Sphere. The capture is guaranteed.

Rewards

Panthalus itself, which is the requirement for World Tree access. Travel to the base of the World Tree and interact with the Altar in front of the barrier to drop it permanently. Three Teafant Springs inside the region restore your and your party's health, at -1895, 1362 · -1723, 1395 · -1536, 1369.

Notes

• Pure Water type. Electric is the only meaningful exploit - there is no secondary weakness to play around.
• You need roughly 590 sustained DPS to burn 353,220 HP inside the 10-minute timer. If the damage is not there, the clock beats you, not the boss.
• The Ring of Mercy has holes. It applies to you and your current mount, but not your active Pal and not passive summons from Partner Skills. Burn and Poison damage over time can still finish Panthalus off, so keep status effects off it entirely.
• Killing it is recoverable. If Panthalus dies the encounter simply ends with no capture - it is not gone for good. Reload the autosave from before you touched the shrine and summon again.
• Defeating it instead of capturing it blocks the World Tree quest until you redo the summon.
• It stays passive until provoked, so there is time to position and mount up before opening.

Not yet cleared first-hand - compiled from external guides. Unconfirmed: what happens when the 10-minute timer expires, and whether Panthalus must be in your active party at the World Tree altar (most sources say no - bring it anyway). Sources also disagree on whether HP hard-locks at 1, which is why the Ring of Mercy is listed as required rather than optional.