Eternity is a Runeword requiring 5 runes, 2 of them extremely rare and expensive (Ber and Sur), and useable in any melee weapon with 5 sockets.
Requirements:
Any Melee Weapon with 5 sockets
Runes (in order): Amn + Ber + Ist + Sol + Sur
The Stats:
Level Reqired: 63
Indestructible
+260-310% Enhanced Damage
+9 To Minimum Damage
7% Life Stolen Per Hit
20% Chance of Crushing Blow
Hit Blinds Target
Slows Target By 33%
Regenerate Mana 16%
Replenish Life +16
Cannot Be Frozen
30% Better Chance Of Getting Magic Items
Level 8 Revive (88 Charges)
Indestructible
With the Indestructible on it, you'd never have to pay a single gold coin to have it repaired ever again. However, since it is very easy to make a lot of money in Hell mode, this should never be main selling point of a weapon.
7% Life Stolen Per Hit
Decent mod, even after factoring in the reduced return in Hell Difficulty. But having no Mana leech as well reduces the usefulness of the Eternity Runeword.
20% Chance of Crushing Blow
This is perhaps the most attractive mod on an Eternity Runeword. Crushing Blow is a modifier that only pops up on Unique, Runewords or Set items. With a successful Crushing Blow on your target, you will reduce their Life by a certain %, which is determined by the weapon you are using, and whether the target is another player, a normal monster or one of the stronger monsters in Diablo 2, ie. Champion, Uniques, Bosses).
Therefore, this mod works best against targets with just-spawned targets with lots of hit points, rather than those who only 10% of Life left. While reducing a monster's current hit points by say, 25%, might not seem a lot, consider that some Uniques and Bosses can have 100,000 hit points or more. A successful Crushing blow will reduce that to 75,000 hit points, while it may take many normal hits to get it down to that.
Crushing Blow can be a good investment for melee characters that don't do huge amounts of damage and thus take a while to kill Bosses, those that do a lot of elemental damage but want to have Crushing Blow as an option against unique monsters that turn out to be immune to their elemental attacks and those who have faster/but weaker attacks.
Equip your character with a weapon that contains the Eternity Runeword (20%) Steelrend Gauntlets (10%), and Goreriders (15%) and you already have a 45% Chance of Crushing Blow, which means that you will trigger Crushing Blow on almost half of your attacks!
Hit Blinds Target
Reduces the ability to hit % of the target to a measly 5% for a short duration. May appear useful at first, but most characters want their monsters to be dead in a shorter period of time. Can be useful for characters with low Life.
Cannot Be Frozen
This mod can be useful if you're going up against monsters that cause cold damage; this modifier prevent makes your character immune to the slowing effects of cold attacks. It does not work against Duriel in Act 2, though.
Summary:
Eternity is one of those Runewords that, by itself, is pretty decent, but which is not very popular with players because there are other Runewords out there that are not only cheaper, but deal more damage (like Grief, for example).
