106.3

Mana is produced by the effects of mana abilities (see rule 605).

Basic lands such as Plains, Island, Swamp, Mountain, and Forest have mana ability. Usualy non-basic land have also.

It may also be produced by the effects of spells,

Dark Ritual is a spell which produce mana.

as well as by the effects of abilities that aren't mana abilities.

Savage Ventmaw's triggered ability and Xenagos, the Reveler's first ability are not mana abilities.

A spell or ability that produces mana instructs a player to add that mana.