A dual-wielding Elven Ninja.
The Elven Ninja is a level 35 monster located in both Elves, and Agara Elves dungeons. It has 105,350 HP, but 0 MP, thus it does not casts spells. They have 565 Defense, and they do about 1250 damage. Furthermore, the monster hits quite hard for a lower level monster and it's recommended to have the best possible armor your current level will allow you to obtain.
The Elven Ninja has a chance of dropping the following:
Elven Essence at a 0.001% drop rate
Snake Katars 0.2% drop rate
Level 25 Armor at a 5% drop rate.