Like in previous FromSoftware RPGs such as Demon's Souls and Dark Souls, magic in the world of Elden Ring can be divided into two rough categories - academic Sorceries powered by the spell-caster's Intelligence and deity-invoking Incantations powered by the spellcaster's faith. Players who want to be able to cast both Sorceries and Incantations will need to heavily upgrade their character's Intelligence and Faith attributes at the expense of the Strength and Dexterity attributes that empower attacks from most melees or ranged weapons; accordingly, creators of hybrid spellcasters in Elden Ring should search for, equip, and upgrade the following "Int/Faith" scaling weapons and magic catalysts.
A key bit of context - there are four character attributes that can influence the damage a player character does in FromSoftware's open-world Elden Ring RPG. First is the Strength attribute, which players upgrade in order to wield and deal damage with large, heavy weapons capable of stunning opponents with every strike. Next is the Dexterity attribute, generally upgraded in order to augment light weapons with swift strikes. The Intelligence attribute generally is used to boost the power of Glintstone Sorceries, a secular magical art capable of manifesting crystals, meteorites, ice, solid light, gravity, and other cosmic phenomena. Finally, the Faith attribute, in most cases, influences the strength of Incantations, a D&D Cleric-style magic of healing miracles and elemental attacks derived from the power of divine entities such as dragons, giants, Outer Gods, or the sky-spanning, potentially parasitic Erdtree of Elden Ring seen from nearly every location in the Lands Between.
In order to maximize both damage and durability of their Tarnished PC, experienced players of Elden Ring frequently create character builds specializing in one particular "attack attribute." To make a character build in the style of a Dungeons & Dragons Fighter, for instance, players will predominantly upgrade their Strength, while Rogue, Wizard, or Cleric-style characters will upgrade their Dexterity, Intelligence, or Faith attributes respectively. Pure Wizard or pure Cleric characters in Elden Ring have access to several weapons and powerful Elden Ring Ashes of War that scale off their Intelligence or Faith, letting them deal a respectable amount of damage to enemies and bosses in point-blank combat. Only a few weapons and spell-casting tools in Elden Ring scale off of both Intelligence and Faith; these pieces of equipment, however, can be very useful tools in the hands of Tarnished characters who wield hybrid schools of magic such as Golden Order Incantations or Death Sorceries.
Elden Ring's Sword Of Night & Flame, Clayman's Harpoon, Erdstreel Dagger
Technically, there is only one weapon in the main game of Elden Ring that can scale with both Intelligence and Faith - Elden Ring's Sword of Night and Flame, a Legendary Armament found in the Caria Manor dungeons within the Liurnia of the Lakes region. This ornate straight sword weapon, said to have been forged by astrologers who lived in the mountains alongside giants, scales well off of both Intelligence and Faith and has a special Skill called Night-and-Flame Stance where Elden Ring characters can fire off either a broad blast of crimson flame or a blue beam of cosmic light.
The Clayman's Harpoon, a spear randomly dropped from the stone-skinned Clayman enemies found in the Siofra River and other underground areas in Elden Ring, scales off of Strength, Dexterity, and Intelligence by default. Similarly, completing the Kenneth Haight quest in Elden Ring's optional boss-laden Limgrave area nets players the Erdsteel Dagger, which scales off of Strength, Dexterity, and Faith by default. Unlike most Intelligence and Faith-scaling weapons found in Elden Ring, the Clayman's Harpoon and Erdsteel can be modified to scale off of both Intelligence AND Faith if players the right Ash of War or use the right Whetblade (though the scaling of the Clayman's Harpoon is somewhat better when fully upgraded).
Elden Ring's Golden Order Seal, Gelmir Glintstone Staff, Prince Of Death's Staff, Frenzied Flame Seal
There are three schools of magic in Elden Ring that require heavy investment into both the Intelligence and Faith attributes. The Golden Order schools of Incantations can conjure lethal rings of holy light and dispel hostile status effects; in the loaded lore of Elden Ring, Golden Order Incantations are the favored discipline of legendary characters such as Radagon, Miquella, and Goldmask, who use scholarship and science to understand, master, and alter the metaphysical laws of reality. The Magma school of Sorceries, themed around conjuring and hurling gouts of magma, are the favored magic of the Volcano Manor, a cabal of assassins who pride themselves on embracing all manner of blasphemous powers in order to destroy the Erdtree and overthrow the Greater Will. Lastly, there is the school of Death Sorcery, a wraith-conjuring discipline both old and new to the Lands Between. In ancient times, before the blooming of the Erdtree, priests of the Death Rite Birds used holy sorceries to cremate the dead and guide lost souls to reincarnation; after the Night of the Black Knives, Death Sorcery was adopted by worshipers of the murdered Godwyn the Golden, whose corpse is bloating, mutating, and causing the dead to rise from their graves.
Each of these "Int/Faith" schools of magic is associated with a specific magical catalyst item players can find during their Elden Ring playthrough. The Golden Order Seal can cast any Incantation, but scales well with Intelligence and Faith while also boosting the effects of Elden Ring's Golden Order Incantations. Similarly, the Gelmir Glintstone Staff and Prince of Death's Staff have Int/Faith scaling and respectively grant bonuses to Magma Sorcery and Death Sorcery attacks.
There is also the Frenzied Flame Seal, bestowed on the players by the NPC Hyetta after completing one of the more "evil" and nihilistic quests in Elden Ring's main game. This sacred seal, which boosts damage dealt by Frenzied Flame Incantations, stands out by virtue of having no minimum stat requirements and for scaling off of every single attack attribute in the game - Strength, Dexterity, Intelligence AND Faith.
By equipping the Golden Order Seal or Frenzied Flame Seal to one hand and Gelmir or Prince of Death Staff to another hand, hybrid spell-casting characters can wield both Elden Ring's Sorceries and Incantation magic in tandem, giving them a versatile bag of tricks in-game enemies and players in PvP will be hard-pressed to match.