The Blue Tablet is in the Lava Castle, guarded by a Ghost Leviathan

The Blue Tablet sits inside the Lava Castle in the Lava Zone, one of the deepest biomes in Subnautica. You cannot straightforward walk in and grab it—a Ghost Leviathan patrols the entrance, and the tablet itself sits in a locked room that requires a Purple Tablet to open. This means you need to collect the Purple Tablet first, then return to the Lava Castle with both the Purple Tablet and a vehicle capable of surviving extreme heat and pressure.

The Lava Castle is located at coordinates 1,258, -1,100, -200 (or search for it by descending into the Lava Zone and looking for the massive structure made of bone-like pillars). The journey down is dangerous: the Lava Zone itself sits at depths beyond 1,300 meters, and the Ghost Leviathan will attack if you get too close. Most players use a Prawn Suit with a drill arm to break through the entrance or a Neptune Rocket as a last resort, though the Prawn is the standard choice.

Key Takeaways

  • You must collect the Purple Tablet before you can reach the Blue Tablet, since the locked door in the Lava Castle requires it.
  • The Ghost Leviathan at the Lava Castle entrance will attack your vehicle, so bring a Prawn Suit with a drill arm or stay out of its detection range.
  • The Lava Castle sits at coordinates 1,258, -1,100, -200 in the Lava Zone, deeper than 1,300 meters below sea level.
  • Once inside, use the Purple Tablet on the locked door, grab the Blue Tablet from the chamber, and leave when ready before the Ghost Leviathan corners you.

Get the Purple Tablet First

The Purple Tablet is located in the Inactive Lava Zone, which is easier to reach than the Lava Castle itself. You will find it inside a structure at coordinates 1,100, -1,300, -400. The path to the Purple Tablet does not require combat—you can navigate around threats or use a Seamoth if you are careful about depth limits.

Once you have the Purple Tablet, you can return to your base or a safe location to prepare for the Lava Castle run. The Purple Tablet is a single-use item that opens the locked door inside the Lava Castle, so do not lose it or drop it in the lava. Store it in your inventory before you descend.

Build or Obtain a Prawn Suit

A Prawn Suit is the best vehicle for reaching the Blue Tablet. It can withstand the heat of the Lava Zone, move quickly enough to avoid the Ghost Leviathan, and drill through obstacles. To build one, you need a Mobile Vehicle Bay in your base and the following materials: titanium, aerogel, plasteel, and a Depth Module Mark 2 upgrade (which lets it survive depths beyond 1,300 meters).

If you do not have a Mobile Vehicle Bay yet, construct one in your base using 1 titanium, 2 aerogel, 1 plasteel, and 1 computer chip. Then build the Prawn Suit inside it. Equip the Prawn with a Drill Arm (not a grappling arm) so you can break through the bone-like walls blocking the entrance to the Lava Castle. The Drill Arm requires titanium, diamond, and lithium to craft.

Bring the Prawn Suit down to the Lava Zone in your Neptune Rocket or by piloting it down yourself if you have the depth upgrades installed. The Prawn Suit can reach the Lava Zone without a rocket, but the rocket is faster and safer.

Navigate Past the Ghost Leviathan

The Ghost Leviathan at the Lava Castle entrance is aggressive but not invincible. It will attack if you get within its detection range, which is roughly 100 meters. Your goal is to either avoid it entirely or move fast enough that it cannot catch you before you reach the entrance.

The safest approach is to approach the Lava Castle from the side or bottom, staying outside the Ghost Leviathan's patrol area. Use your Prawn Suit's speed to move in, drill through the entrance wall, and get inside the structure before the creature can intercept you. If the Ghost Leviathan does attack, your Prawn Suit can take several hits—do not panic. Keep moving toward the entrance and do not stop to fight.

Once you are inside the Lava Castle, the Ghost Leviathan cannot follow you through the narrow passages. You are safe to explore and locate the locked door.

Use the Purple Tablet and Collect the Blue Tablet

Inside the Lava Castle, navigate through the bone corridors until you find a locked door with a purple slot. This is where you use the Purple Tablet. Approach the door, and a prompt will appear—interact with it to unlock the chamber.

The Blue Tablet sits on a pedestal inside the unlocked room. Walk up to it and take it into your inventory. The tablet is yours—no combat or puzzle is required once the door is open. The entire chamber is safe; there are no creatures inside.

Exit the Lava Castle Safely

After collecting the Blue Tablet, retrace your steps back to the entrance of the Lava Castle. The Ghost Leviathan may still be patrolling outside, but you can exit the same way you entered. Use your Prawn Suit's speed to move away from the structure and gain distance from the creature.

Once you are clear of the Lava Zone, you can pilot your Prawn Suit back to your base or to the Neptune Rocket if you used one to descend. Store the Blue Tablet in a safe location—you will need it later to unlock doors in the Primary Containment Facility and other end-game areas.

Common Mistakes to Avoid

Do not attempt the Lava Castle without the Purple Tablet. The locked door cannot be opened any other way, and you will waste time and resources. Collect the Purple Tablet from the Inactive Lava Zone first.

Do not bring a Seamoth or Cyclops to the Lava Castle. The Seamoth cannot survive the depth or heat, and the Cyclops is too large to fit through the narrow entrance passages. A Prawn Suit is the correct vehicle for this mission.

Do not fight the Ghost Leviathan directly. Your goal is to avoid it or move past it quickly. Fighting wastes time and damages your Prawn Suit. Speed and evasion are your best tools.

Do not drop the Purple Tablet in the lava or lose it before you reach the locked door. If you do, you will have to return to the Inactive Lava Zone to get another one. Keep it in your inventory at all times during the descent.

Frequently Asked Questions

Can I get the Blue Tablet without a Prawn Suit?

No. The Lava Zone is too deep and hot for a Seamoth, and the Cyclops cannot fit through the entrance. A Prawn Suit with depth upgrades is the only vehicle that can reach the Lava Castle and navigate inside it. You can also use the Neptune Rocket to descend, but you still need a Prawn Suit to enter the structure.

What happens if the Ghost Leviathan kills me?

You will respawn at your last safe location (usually your base or a pod). Your Prawn Suit will remain where it was, and you can return to retrieve it. The Ghost Leviathan does not despawn, so you will need to approach the Lava Castle again and repeat the evasion strategy.

Do I need the Blue Tablet to beat the game?

Yes. The Blue Tablet is required to unlock doors in the Primary Containment Facility, which is necessary to reach the end-game content and complete the story. You cannot progress without it.

Can I get the Blue Tablet before the Purple Tablet?

No. The locked door inside the Lava Castle requires the Purple Tablet to open. You must collect the Purple Tablet from the Inactive Lava Zone first, then return to the Lava Castle with it.

Is there a way to avoid the Ghost Leviathan entirely?

You can approach the Lava Castle from angles where the Ghost Leviathan does not patrol, or you can move fast enough that it does not catch you. Some players use the Neptune Rocket to descend directly into the structure, which bypasses the need to navigate past the creature on the surface.