To get to the island, head out to Batallia Downs, go to (I-10) inside the small cave, and enter Eldieme Necropolis. Your goal is to get to (G-9). To do this, you must have at least a duo in order to operate the gates.
There are switches that manipulate all the gates at each of the 4 main sections with graves in them. Two will be available at the start; they are at (H-8) and (F-8).
Have someone move to (H-9) where the lich spawns and have them face the south closed gate (it should be named Titan's Gate).
Once there, have the person at the switch open Titan's gate for you. Once through the gate, run to the switch in your area at (G-9).
Now whoever is at the (G-9) switch must open and close the gates for the person at the other switch.
Once everyone is now gathered at (G-9), find the grave in the middle of the 9 graves and walk over it (If lich and tomb wolves aggro, you must put Sneak up first) and fall through the hole.
Once you're down the hole, follow the path until you end up at a fork. Turn right here and proceed south until you find the zone at (J-9) to Batallia.