If its the tombstone deep underground near the starting area...
Explore a lot, find some book item (maybe found after a boss fight or something). Give it to one of the robed people sitting outside the "random generated" dungeon you fight mobs at entrance.
He will give you a new selection of items. You will need a 10g bottle from a NPC at the 3rd town, and a coral item found at the same level with the goblin boss (there is a water cave in the area with fish monsters and ice wolves). In that cave, you will get a coral.
With the coral+ bottle, go back to the NPC earlier, he has a greenish bottle looking item for sale, but it and now you will have a bigger "light"/lantern thing. Go back to the tomb in the beginning area, talk to the tombstone again, and then go to your left, now you can go across the water and become a dark elf.
Extra stuff
After this, go to the 2nd town (not sure on order), talk to the girl that used to be in your party, then talk to the robed guy on the upper right of town near some blue pentagram. He will leave, and then go back to the girl, she will move to the room. Randomly select options, get a R-18 scene.. she will rejoin group.
Anyone figure a way to corrupt the 2nd girl faster than... loosing to a battle with her over and over and over....
Also, anyone figure how to go to the 2nd floor of the spa place?