Forget Skorne, the Shadow Wraith is even tougher than he is! In fact, only the final boss, Garm is as hard as the Wraith and only arguably so.
Attempting the battle at anything less than Level 80 is foolhardy, even at Level 99 you have to watch your health. Having the Lantern helps, but it really only buys you time form the Wraith's most damaging attacks.
The Wraith hits you hard and fast right at the start, his attacks to watch out for in particular, are his shadow tendril strikes and his green-black shadow bomb. This bomb can take out as much 400-500 health if it hits you!
It also doesn't help that the arena you're fighting him in is small.
If you're not good at dodging, you'll need to dig deep at the store for Invulnerability power-ups, at least 8 or so. 3-Way Shots, Rapid Fires, and Super Shots are also important and coupled with Light Amulets, are the key to beating the Wraith (somewhat) quickly.