Kindred is a card type that allows noncreature cards to have creature types. For example, Echoes of Eternity is an Eldrazi (although not a creature) while on the battlefield and an Eldrazi card (although not a creature card) in zones other than the battlefield.
While it appears only on cards that already have other card types, kindred is a card type and will be counted by effects that refer to the number of card types among cards in a zone.
This cards was originally printed with the "tribal" card type. That card type has been replaced with "kindred". This change does not affect the gameplay function of this card.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Yeong-Hao Han
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If Altar of the Goyf somehow becomes a creature and the effect allows to keep its other types, it will give itself trample.
A creature attacks alone if it's the only creature declared as an attacker during the declare attackers step (including creatures controlled by your teammates, if applicable). For example, Altar of the Goyf's first ability won't trigger if you attack with multiple creatures and all but one of them are removed from combat.
The card types that can appear in a graveyard are artifact, battle, creature, enchantment, instant, kindred, land, planeswalker, and sorcery. Legendary, basic, and snow are supertypes, not card types; Aura and Lhurgoyf are subtypes, not card types.
