From Medivia Online Wiki
Near City: Ab'Dendriel
Location: North west of Ab'Dendriel, Elf Scout, Elf Sharpshooter (Thaian Faction) and Elf Guardian (Thaian Faction) task.
Loot: Yellow Gem, Elven Bow, Platinum Amulet, Spike Sword, Guardian Shield, Light Sword and Hunting Boware the loots with he highest value, while longsword, broad Sword, two handed sword, bow, Elven Amulet and Life Crystal can be gathered for lootbags.
Warriors: Never forget to carry some Ultimate Healing Rune with you, unlike Shadowthorn, you will have to fight Elf Guardian to hunt here. It is important not to rush the area, or you could be overrun by a lot of strong enemies, this can be hard with Elf Sharpshooters running away, so be sure to know where to corner them and exactly where each spawn is. There might be some times where it is better to use Great Fireball runes to clear all the monsters instead of tanking all of them and killing one by one, so bring the runes. Also, if you want to kill the Elf Arcanist faster, Explosion are the only option.
Scouts: Since you will loot a lot of arrowand hunting arrow here, it is advisable to use a bowinstead of a crossbow, and in addition to that all elves except for the arcanists can be affected by any of the 3 Distance Weapons. For your safety, bring Ultimate Healing Rune and also Great Fireball to avoid waste. Spears are also a good alternative and stair hopping can be effective against the Elf Swordmaster.
*For all classes: Elf Swordmaster run away when on low HP and have no healing, so you can just leaving them that way, instead of killing, it is a great alternative to avoid waste.
Location and Route:
Accessing the cave is extremely easy as it is already inside the city of Ab'dendriel (see below):
Once Inside, there are 2 holes that lead to different areas, one is a hallway full of Elf Guardian and the other is the larger area of the cave, which is also the most dangerous.
Inside the cave:
Following you can see the maps for the entire cave and all of its spawns: