Apart from its difficulty, Elden Ring is also famed for giving players tons of opportunities to customize their weapons and character builds. Their weapon skill system has been expanded and has gotten more intricate, building upon Dark Souls 3's weapon art system. Now, weapon prefix affinities can also be customized through the Ash of War (weapon skill).
This diversifies the number of available builds to dizzying layers of variety. Some weapon prefix affinities are also heavily dependent on the Ashes of War skill itself, meaning they might not be available for certain weapons. At times, this system can even be intimidating so here's a rundown of what to understand about the weapon prefix affinity system in Elden Ring and an approximation of how useful or viable they are in the meta.
13 Occult
- Scaling: Arcane, decreases all other scaling
- Available weapons: Swords, Axes, & Hammers
Occult might be best-used for Arcane builds that are in need of a backup weapon other than Bleed weapons. Because those with high Arcane stats will benefit the most from this weapon. Even so, it's easily overshadowed by the Blood prefix affinity which not only increases Arcane weapon damage but also adds more Bleed.
12 Flame
- Scaling: Faith, decreases default weapon scaling and adds Fire damage
- Available weapons: Depends on the Ash of War
The Flame prefix affinity might look appealing since it doesn't modify the weapon's default scaling and also adds Fire to the attacks but the weapons and the Ashes of War for it are rather limited. It's only available for Prelate's Charge and Black Flame Tornado.
11 Fire
- Scaling: Decreases default weapon scaling and adds Fire damage
- Available weapons: Most melee weapons
Fire prefix affinity is the less appealing version of the Flame prefix except it's also a bit worse since it tampers with the default weapon scaling. Moreover, that split Fire damage is not that good since the sum of the damage might get lower as it will have to pass through two resistances.
10 Poison
- Scaling: Strength, Dexterity, & Arcane
- Available weapons: Most melee weapons
Poison builds will have a field day with this one as it's practically a buff for the weapons and will also make them deal poison buildup. It does, however, make the scaling a bit hard to manage since it's split into three, meaning a delicate balance between physical damage (Str/Dex) and poison damage-over-time (Arcane) will have to be achieved. And even then, there might be enemies who are immune or resistant to poison.
9 Lightning
- Scaling: Dexterity, decreases Strength scaling and base damage, adds Lightning damage
- Available weapons: Swords, Katanas, Greatswords, Curved Swords, Double-Edged Swords, Spears, Great Spears, Hammers, & Axes
Those expecting the Lightning prefix to scale with Faith will be disappointed. This one scales with Dexterity, surprisingly. The added Lightning damage is also a good bonus here but most Dex builds will probably benefit more from Bleed weapons or the Keen prefix.
8 Sacred
- Scaling: Faith, decreases physical damage, adds Holy damage
- Available weapons: Depends on the Ash of War, most weapons
As expected, the Sacred upgrade for weapons is best used for Paladin or melee Faith builds. There are lots of great buff Incantations that make this prefix desirable, 
Golden Vow being one of them. While the split damage and Holy damage type fall off late-game, it's a great tool for mopping up undead enemies.
7 Magic
- Scaling: Intelligence, decreases Strength/Dexterity scaling along with base damage, adds Magic damage
- Available weapons: Swords, Katanas, Greatswords, Curved Swords, Double-Edged Swords, Spears, Great Spears, Hammers, and Axes
The Magic prefix is perfect for wizards and mages who are tired of spewing ranged spells and want to get up close and personal. This upgrade turns any melee weapon into a spellblade's Swiss knife where even some melee weapons can have spells attached to them as the weapon skill.
6 Cold
- Scaling: Intelligence, decreases all other scaling, adds Frostbite buildup
- Available weapons: Depends on the Ash of War
Cold damage is one of the more underrated prefix affinities in Elden Ring as many people underestimate Frostbite's usefulness in both PvE and PvP. However, it can be just as damaging as Bleed. Even a Cold Uchigatana can be brought to late-game environments and it will still wreck bosses.
5 Standard
- Scaling: Item default
- Available weapons: All Weapons and Shields
Standard doesn't really change anything and allows players to use the weapon's original intended scaling. But it has the added benefit of having better availability across a wide range of items. For players who are still undecided on which direction they want to take their weapon upgrades, then this prefix might be the better choice.
4 Heavy
- Scaling: Strength, decreases all other scaling
- Available weapons: Swords (minus small & medium swords), Axes, & Hammers
Those who have decided that their characters will channel their inner cavemen and just bonk enemies to death will benefit the most from this prefix. It takes advantage of high Strength values, making the playstyle rather simple and less confusing. It's best used on heavy weapons, for that matter, but even some of the smaller axes can be converted to intimidating bonk sticks.