I had rough times dealing with "Venom Swamp" effect during Chile's Tactical Evolution Sneak Preview event.
I know it's mandatory, but...is the turn player who choses when to activate the effect, or is the controller? For example...could the controller activate "Venom Swamp"'s effect, and then return to the field a monster removed by "Interdimensional Matter Transporter", so the monster be "saved" from the "Venom Swamp" effect?
Response:
The Turn Player has the right to activate effects in their End Phase before applying "Venom Swamp's" effect, however the effect of "Venom Swamp" needs to be handled during the End Phase. The turn won't end until it has been applied.
If the Turn Player happens to be under control of the "Venom Swamp", they could certainly apply its effect right away or use other effects before applying the "Venom Swamp".
This shouldn't become overcomplicated. Both players know that it needs to be done. The only thing that really needs to be decided is if anyone will activate any other effects before applying "Venom Swamp's" effect.
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Curtis Schultz
UDE Netrep
CurtisSchultz_Netrep@hotmail.com