This is an Ignition Effect.
You can select a face-up or face-down monster to remove from play. A face-down monster removed with this effect will remain face-down while removed from play. So if a face-down
"D.D. Scout Plane" is removed from play, its effect will not activate.
Returning the monster to play cannot be chained to. The effect will resolve and the monster will return to play during your 2nd Standby Phase even if
"Destiny Hero - Doom Lord" is no longer on the field or is flipped face-down (even as a chain to the activation of his effect).
If your 2nd Standby Phase is skipped by the effect of a card like
"Solomon’s Lawbook", then the removed monster will never return to play.
You can activate
"Destiny Hero - Doom Lord’s" effect even if your Battle Phase is going to be skipped because of a card effect like
"Soul Exchange".
If you declared an attack then you cannot activate
"Destiny Hero - Doom Lord’s" effect this turn, even if your only attack was negated.
If you have both
"Destiny Hero - Doom Lord" and
"Berserk Gorilla" face-up on the field you can still activate
"Doom Lord’s" effect.
"Berserk Gorilla" will not be able to attack that turn.
If all 5 of your opponent’s Monster Card Zones are full when the removed monster would return to play, it is destroyed.