The Occult upgrade path is a form of weapon ascension. Andre of Astora gains the ability to upgrade weapons down its path after receiving the Dark Ember. Creation of an Occult weapon requires a +5 Divine weapon (which in turn requires a standard weapon +5) and a White Titanite Chunk. Upgrading an Occult weapon further requires White Titanite Chunks to +4, and a White Titanite Slab to upgrade to +5.
The Occult upgrade path adds the Occult auxiliary effect, increases scaling with Faith and adds Magic Damage to weapons, but reduces Dexterity and Strength scaling. This makes Occult weapons suitable for players that have high faith, but low Strength and Dexterity. Occult weapons have an even higher scaling with Faith than Divine weapons, but curbs Dexterity and Strength parameter bonuses more severely.
Occult weapons cannot be augmented. At high levels of Strength/Dexterity and Faith, a standard weapon enchanted with a Miracle such as Sunlight Blade or Darkmoon Blade, or the Crystal Magic Weapon Sorcery will out-damage Occult weapons in the short run. However, Occult weapons hold the advantage of not having to be enchanted to reach their maximum potential. Unlike Divine weapons, Occult weapons cannot be used to permanently kill skeletons found in The Catacombs and the Tomb of the Giants.