Because “Dark Master - Zorc”’s effect is a Ignition Effect, you roll the die during Main Phase 1 or 2 of your turn only.
If you roll a 6, “Dark Master - Zorc” is also destroyed.
Netrep Q&As:
Q: When is the target for “Dark Master – Zorc” chosen and will the effect be considered targeting if the dice roll is 3, 4, or 5?
A: You would have to choose your target during resolution. When you activate the effect of “Dark Master - Zorc,” you have no idea what is going to happen. Due to this, the effect cannot declare any target at activation. Curtis Schultz, 02/15/2004