Useful on multiple facets, Hellplague is a fascinating sword. On the physical end, Hellplague's strength lies in its elemental damage. Although its damage without bonuses may seem lackluster (with a particularly low minimum damage), Hellplague bestows a very high amount of Fire damage, as well as Poison damage. Although certainly not as effective against enemies immune to either Fire, Poison, or both, Hellplague can still do a good amount of damage against those who aren't.
Hellplague also bestows both life and mana leech. Physical fighters such as Barbarians or Amazons, who use mana-consuming skills, but often don't typically invest in Energy, would especially find mana leech useful.
However, most interesting is Hellplague's bonuses to Fire Skills. Besides a Sorceress' Fire Spells or a Druid's Elemental Skills, not many characters have a wide variety of fire skills. However, the Paladin does have Holy Fire, and considering that they are most likely to use either swords or Maces, Hellplague may be better off in the hands of a Paladin.
Another possible use is in combination with Enchant. Since Hellplague does decent damage and would give a boost to Enchant, it could be used by Sorceresses to have a more effective Enchant.
One-Hand Damage: 5 To (32-34)
Required Level: 22
Required Strength: 55
Required Dexterity: 39
Sword Class - Fast Attack Speed
+70-80% Enhanced Damage
+2 To Fire Skills
Adds 25-75 Fire Damage
Adds 28-56 Poison Damage Over 6 Seconds
5% Life Stolen Per Hit
5% Mana Stolen Per Hit