I have trouble writing this effect:
Is this correct OCG/PSCT?
- Destroy all Set monsters your opponent controls, and if you do, your opponent loses 700 LP for each.
When you have an effect that attempts to apply to all cards in a given place and it's followed by "and if you do" or "then", you say "as many [cards] as possible" instead of "all [cards]". This clarifies that you don't have to have destroyed all Set monsters your opponent controls to proceed beyond "and if you do" because some might be unable to be destroyed by card effects. That is, you apply what's functionally identical to "destroy all Set monsters your opponent controls," but proceed beyond "and if you do" even if not every monster it could've affected was destroyed.
So in this case it would be "Destroy as many Set monsters your opponent controls as possible."
You want to say "inflict 700 damage to your opponent for each" instead, losing LP is only used when talking about yourself. Also, I would say "for each card destroyed", though I have seen some cards that omit that too, I just prefer it since it makes it a bit clearer.
Losing LP isn't restricted mechanically or conventionally restricted to something you can only do to yourself. See Contract with Don Thousand.
Regardless you should still generally have card effects inflict damage to your opponent instead of making them lose LP. Only have them lose LP instead of taking damage if there's a reason to.
I don't know whether Lurkers do or not, but there's too much we don't know about them for me to make a comment on a thread like this. (What's the significance of declaring a number for the ATK-gaining effect below if it's, from what we know, almost always better to declare the highest number, for instance?)
I have trouble wording this effect:
This is an effect for my archetype "Lurker". What it does is that the player declares a number from 1 to 10 inclusive, and the card gains ATK and DEF equal to the declared number x some other number until the end of this turn.
- Declare a number from 1 to 10; this card gains ATK and DEF equal to the declared number x 900 until the end of this turn.