Hi, i would like to clear this point:
If a monster like "Thestalos the Firestorm Monarch" or "White-Horned Dragon" with Mandatory Trigger Effect, is summoned, but the opponent has no cards in their hand (for the first) or has no spells in their graveyard (for the second) would the effect activate normally, going on chain and then disappearing, or it doesn't activate at all?
Answer:
I cannot say what will occur in every possible instance, because there are far too many cards and there may be some that act differently, but I can speak for these two.
"Thestalos the Firestorm Monarch's" effect will not activate if the opponent has no cards in their hand at the time it is successfully Tribute Summoned.
For "White-Horned Dragon", if your opponent does not have any Spell Cards in the Graveyard when you Normal Summon or Special Summon it, you cannot select any Spell Cards to remove so the effect won't activate.
Some mandatory trigger effects have costs, and if you cannot pay the cost you cannot activate the effect. Costs must be paid in order to activate an effect, so it makes sense that you cannot activate the effect if you cannot pay the cost.
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Curtis Schultz
Official UDE Rules Dude
CurtisSchultz_Netrep@Hotmail.com