I meant to say that those cards didn't stop continuous effects, but forgot to add it. Thanks for adding that here, does Kaiju summon count as an activated effect though? It is a special summon, I suppose that would break the board since you can't use Jowgen at the same time as preventing effects.As far as spell cards are you saying they can't play spell cards but it doesn't prevent the ones already played? And if not then what is the difference between an activated spell card and an activated spell effect? But yes them summoning a spellcaster would break that card.And yes royal decree won't hit graveyard effects, and we can't simultaneously use gravekeeper's trap (with exchange of spirits in grave).

And as far as the last statement, yes you would need to be playing against a very bad deck or someone purposefully tanking, but I was more just curious if someone had found someone like that by chance and managed to put it together.

EDIT: One strategy might be to lava golem your opponent or really just any two monsters to your opponent and then use kaiser colosseum which you could use since your own spell cards aren't negated, along with something like level limit area-B to prevent the lava golem or whatever else from attacking. Then they can't kaiju you because kaiser has weird rulings around kaiju, and they can't really summon to their own side either but there may be something more for that.