The Black Halberd
This artifact is about as tough as the Plate of Pachtar. It's also worth it.
The Rakshasa Lair
Learn the location from a man in Sharamik. This dungeon is far North of the dragon lairs, in the mountains. It is not the Defiled crypt with the Vahnati. The first floor contains puzzles. The first one, just go to the white mushrooms and head straight south. Next, push a crate to the rune and look in it. Then, to navigate the pillars, follow the direction on the map, but rotate it so the arrow faces up. Next, play with the runes until six lights are visible. Look at the Stalagmites and take the middle stairway. Go to the East and North, than East into the lair. The key to fighting Rakshasas is to put them in antimagic fields and bless your fighters. It's the only way to make it. Go to the North, take the West door, and take the West door again. Take a secret passage to the West and head North. You'll be ambushed. To the North is the Halebard, and some other goodies. To leave, the the passages marked 'Pain!' They lead to the same place, Drakes and lava. The exit is East.
Here is the Map for the "Black Halberd"