If either player has no monsters in their Graveyard, the effect of this card cannot be activated.
If “Kycoo the Ghost Destroyer” is on the field, the effect of this card cannot be activated.
Paying 500 Life Points is a cost.
You must select the monster in the Graveyard you wish to target when you activate this card’s effect. You select before the opponent does. After you select the opponent may chain, with a card like “Dust Tornado”, to destroy “Soul Demolition”. In this case its effect will not resolve and no monsters will be removed. This is because it is a Continuous Trap Card and it must remain on the field for its effect to resolve. If the effect is negated you do not get a refund of the 500 Life Point cost.
If the opponent chains to the effect of “Soul Demolition” with an effect that destroys all the Fiend-Type monsters on your side of the field, the effect of “Soul Demolition” resolves because the activation conditions were correct at the time.
If you chain the effect of “Soul Demolition” to “Monster Reborn” and remove the monster targeted by “Monster Reborn” from play, the effect of “Monster Reborn” disappears.