Mana source

From MTG Salvation Wiki

Mana source is an obsolete card type that was only found on Culling the Weak and Dark Ritual, as well as the non-tournament-legal Blacker Lotus and Jack-in-the-Mox, beginning with the printing in Mirage until Urza's Saga. All mana sources would have been interrupts under pre-Mirage rules, and are now instants. Abilities that were played as mana sources were previously played as interrupts, and are now mana abilities.

From the Comprehensive Rules Mana Source (Obsolete) Some older cards were printed with the card type “mana source.” All mana source cards are now instant cards. Abilities that used to read “Play this ability as a mana source” are now mana abilities.

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Card types
Groups	Supertypes	Card types	Subtypes
Spell (non-permanent)		Instant	Trap	Arcane
		Sorcery
Permanent	Basic, Legendary, Snow, World	Artifact	Equipment, Fortification, Contraption
		Creature	(...)
		Enchantment	Aura, Shrine
		Land	(...)
		Planeswalker	(...)
Miscellaneous		Tribal	(...)
		Plane	(...)
		Vanguard
Obsolete	Mono, Poly, Continuous	Interrupt, Mana Source