Changeling is a characteristic-defining ability. It functions in all zones, not only while a card that has it is on the battlefield.

Effects that modify a creature's power and/or toughness, such as the effect of Appeal to Eirdu, will apply to the creature no matter when they started to take effect. The same is true for any counters that change its power and/or toughness and effects that switch its power and toughness.

Firdoch Core's last ability overwrites all previous effects that set its base power and toughness to specific values. Any power- or toughness-setting effects that start to apply after the ability resolves will overwrite this effect.

If an effect causes a creature with changeling to become a new creature type, it will be only that new creature type (unless the effect says "in addition" or similar). It will still have changeling; the effect making it all creature types will simply be overwritten.

If an effect causes a creature with changeling to lose all abilities, it will remain all creature types, even though it will no longer have changeling. This is because changeling applies before the effect that removes it.

Kindred is a card type that allows noncreature cards to have creature types. For example, Morcant's Eyes is an Elf (although not a creature) while on the battlefield and an Elf card (although not a creature card) in zones other than the battlefield.

Some older cards were originally printed with the "tribal" card type. That card type has been replaced with "kindred." This change does not affect the gameplay function of these cards.

The subtype Shapeshifter that appears on the type line is mostly there to reinforce the flavor. A creature card with changeling is just as much a Kithkin, a Goblin, a Merfolk, and a Brushwagg as it is a Shapeshifter.

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.