“Castle of Dark Illusions’s” effect will increase the ATK of Zombie monsters on the field by 200 per turn for each turn that “Castle of Dark Illusions” is face-up, for the duration of 4 turns on the Standby Phase.
If “Castle of Dark Illusions” leaves the field before the fourth Standby Phase, the ATK increase will stop increasing. Any ATK increase that occurred as a result of “Castle of Dark Illusions” will remain on the respective Zombie-Type monsters as long as those Zombie-Type remain face up on the field.
Netrep Q&As:
Q: Would my face-up “Spirit Reaper” be destroyed if my “Castle of Dark Illusions” was flipped face-up and do Zombie-Type monsters place on the field face-up after “Castle of Dark Illusions” is face-up receive the increase?
A: “Castle of Dark Illusion’s” effect is not a targetting effect. “Spirit Reaper” will not be destroyed by its effect. Any Zombies brought face-up on the field while “Castle of Dark Illusion’s” effect is active will get the increase. It does not matter if the Zombies were face-up on the field when “Castle of Dark Illusions” was flipped. Curtis Schultz, 12/08/2003