Renegade Silent

At the beginning of your end step, goad up to one target creature you don't control and put a +1/+1 counter on this creature. This creature phases out. (Treat it and anything attached to it as though they don't exist until your next turn.)

Doctor Who

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 and pay a cost of {T} during that turn.

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

As Renegade Silent phases 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 Renegade Silent does, and they'll phase in still attached to Renegade Silent. Similarly, it will phase in with any counters it had on it.

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

If an opponent gains control of your Renegade Silent until end of turn, it will phase out while they still have control of it. The control-changing effect ends while it is phased out, and it phases in under your control as that opponent's next untap step begins. If they leave the game before their next untap step, Renegade Silent phases in as the next untap step begins after their turn would have begun.

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.

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.