Phased-out permanents are treated as though they don't exist. They can't be the targets of spells or abilities, their static abilities have no effect on the game, their triggered abilities can't trigger, they can't attack or block, and so on.

An attacking or blocking creature that phases out is removed from combat.

Phasing out doesn't cause any "leaves the battlefield" abilities to trigger. Similarly, phasing in won't cause any "enters the battlefield" abilities to trigger.

Permanents phase back in during their controller's untap step, immediately before that player untaps their permanents. Creatures that phase in this way are able to attack during that turn, and their activated abilities with {T} in their costs can be activated. If a permanent had counters on it when it phased out, it will have those counters when it phases back in.

As a permanent is phased out, Auras and Equipment attached to it also phase out at the same time. Those Auras and Equipment will phase in at the same time that creature does, and they'll phase in still attached to that permanent.

Any continuous effects with a "for as long as" duration ignore phased-out objects. If ignoring those objects causes the effect's conditions to no longer be met, the duration will expire.

Choices made for permanents as they entered the battlefield are remembered when they phase in.

If you put a permanent with a kicker ability onto the battlefield without casting it, you can't kick it.

To determine a spell's total cost, start with the mana cost (or an alternative cost if another card's effect allows you to pay one instead), add any cost increases (such as kicker), then apply any cost reductions. The spell's mana value remains unchanged, no matter what the total cost to cast it was.

If a spell's kicker cost was paid, the spell is "kicked."

If a card or token enters as a copy of a permanent, the new permanent isn't kicked, even if the original was.

If you copy a kicked spell on the stack, the copy is also kicked. If the copied spell is a permanent spell, the token the copy of that spell becomes when it enters is also kicked.

The kicker ability doesn't let you pay a kicker cost more than once.