Slayer Skin Puzzle
The Slayer Skin is an unlockable skin for the Dark Blade and Triple Dark Blade swords. It changes their appearance and attack effects (without Aura) from green to a black-and-white theme. Once unlocked, the skin can be toggled on or off by speaking to rip_indra at the Graveyard. 
Requirements
Before starting the puzzle, players must have:
Angel V3 or higher
Human V3 or higher
Rabbit V3 or higher
Shark V3 or higher
2 Fists of Darkness
1 to summon Darkbeard
1 to open the Graveyard door
Note: If another player has already unlocked the Slayer Skin in the current server, it cannot be obtained again. You can check this by visiting the Graveyard—if the gateway is already white, the puzzle has already been completed on that server.
How to Unlock Slayer Skin - Puzzle Walkthrough
Step 1 – Summon Darkbeard
Have one player use a Fist of Darkness to start a Darkbeard Raid.
At the same time, another player should stand at the Graveyard door while holding the second Fist of Darkness.
Location
Dark Arena
Step 2 – Open the Secret Door
With the Fist of Darkness in your hotbar:
Unequip all items.
Press the button beside the Graveyard door.
The door will open, revealing a bright white gateway.
Location
Graveyard
Step 3 – Unlock the Slayer Skin
When the door opens, the following message will appear in the chat:
"A NEW SLAYER HAS BEEN BORN"
The player will immediately receive:
Slayer Skin for the Dark Blade and Triple Dark Blade
"Slayer of God" Title (#151)