Beast Runeword

Beast is one of the two runewords in Diablo 2: Resurrected that provides the player equipping it with a Fanaticism aura. While the level of the aura is lower than the one on Faith, its counterpart, Beast still has several advantages over Faith.

First, let’s look at the runeword and what it offers:

        Ber+Tir+Um+Mal+Lum

Level 9 Fanaticism Aura When Equipped
+40% Increased Attack Speed
+240-270% Enhanced Damage
+20% Chance of Crushing Blow
+25% Chance of Open Wounds
+3 To Werebear
+3 To Lycanthropy
Prevent Monster Heal
+25-40 To Strength
+10 To Energy
+2 To Mana After Each Kill
Level 13 Summon Grizzly (5 Charges)

The level 9 Fanaticism Aura is clearly the most eye-catching line here. It translates to 186% more damage for the character equipping it, 93% for the party, 29% Increased Attack Speed, and a whopping 80% increase to Attack Rating.
To compensate for this, the Enhanced Damage roll on the weapon is lower than what we normally see on runewords made out of similarly rare High Runes. Breath of the Dying goes all the way up to 400, Death reaches 385, and Grief has a huge flat added damage bonus instead that makes it incredible in fast-hitting weapons such as Phase Blades.
The 40% IAS is great, since weapon attack speed is usually more important than attack speed from other sources. 
As always, a bonus to Strength for up to 40 makes gearing much easier, and will save every character a good chunk of stat points to put into Vitality instead.
The Ber and Mal runes in the runeword carry with them the Crushing Blow and Open Wounds procs. These are incredibly useful against bosses, since CB can chunk their health down very quickly, whereas OW makes them unable to regenerate health during its 8 second duration.
The Werebear and Lycanthropy oskills (bonus skills that every character class can use, not just Druids) are an interesting addition, as being a Werebear has both up-and downsides. It provides the character with increased damage and defense, while Lycanthropy also gives you increased life on top of it. On the other hand, it will disable all non-Werebear skills, which means that without being a Druid, the only available skill to use is going to be the plain old Normal Attack. This results in losing out on Area of Effect attacks like Whirlwind, or attacks that provide Attack Rating, Damage or Attack Speed bonuses such as Frenzy, or Zeal.

Knowing exactly what we get out of Beast, we can now take a look at who might benefit from it the most.
For Barbarians, it’s a somewhat popular choice, because people love quick attacks with Fanaticism. Beast has a few major downsides compared to the more optimal picks, however. Not featuring Indestructible or Self-Repairing, Beast can only be placed in non-ethereal weapons. This means that not only is the weapon damage going to be a lot lower than ethereal BotDs or Deaths, the rapid attacks of Whirlwind and Frenzy also wear out the weapon very quickly. Having to repair your weapon often is not only an inconvenience, it also costs a lot of gold in the case of higher tier runewords made in elite weapons. 
Moreover, the lack of a Life Leech roll makes it a must-have on the other weapon instead, which limits our choices to either BotD or Last Wish.
An interesting build that runs Beast is the Bear Sorceress. While it is not a very popular build, it is surprisingly decent if you don’t expect a clear speed that rivals Javazons or Hammerdins, and don’t mind a lot of micro-management. It is fun to play and fairly strong, but very expensive and requires a lot of gear swapping to make it optimal. It is also restricted to normal attacks only, while a double Dream setup tries to make up for the lack of AoE.

By far the best use for a Beast weapon is a summoner Necromancer. While the alternative to it, the Arm of King Leoric offers a huge +5 to all the relevant summoning skills and some other beneficial stats, the Fanaticism Aura more than makes up for it. To this end, it is best to put Beast in a normal weapon with low requirements, such as a War Axe or a Double Axe.

All in all, Beast is a curious runeword that might originally have been intended to be a great weapon for big brawny Barbarians and Paladins, while also offering some extra flavor. Even if it did not quite reach that potential, it instead became a great supporting weapon for summoned armies, and Sorceresses itching to get up close and personal. A very fun item nonetheless, and easily worth the price of a Ber rune.