Since the lauch of the First Chaotic Throne, there are two quest which are needed to do to be able to enter Hellbound are of Lineage 2.

Familiar with Gludio's Warpgate guarded by Jirone and Heine's Warpgate guarded by Galate? Well, thats the only two portals for Hellbound, you cannot go and swim directly to the island and climb up, Hellbound is surrounded by high and steep cliffs, which cannot be climbed.

Getting the warpgate activated:

You can go to Isle of Prayer to start the long quest. Speak to Priest Kanis to start the process.

You must do the two quests, namely, "That's Bloody Hot!" and "Bird in a Cage" (must do it consecutively as enumeratted).
Click on the blue links to acces the quests.

After finishing both quests... you must kill Baylor...

Before you proceed killing Baylor, you must to Dark Cloud Mansion quest, an instanced dungeon quest offered by Archeologist Yiyen. This is a time limit quest to obtain contaminated crystal in order to access the 4 instanced dungeon in Island Of Prayer. The location of Yiyen is near Chromatic Highlands. check you Map, Quest Tab for details and location.

You need to defeat 3 Raid Bosses first in the instanced dungeon before facing Baylor in Emeral Square.

After defeating him, an Oracle Guide will appear... this will port u to Parme way up high to Baylors lair.

Congratulations, You can now port to Hellbound via the Warpgates.

NOTE: Starting with Gracia, it`s much easier to acces Hellbound.