"The effect of Tour Guide from the Underworld doesn't resolve when trap hole is activated destroying it."
This is absolutly the wrong idea here.
"Priority is based on the card's effect."
Also wrong.
Priority is not based on a card at all it is a built in game mechanic based on the chaining system between player and opponent.
How the tour guide play actually plays out based on this system.
Tour Guide is summoned
1. Turn player may negate the summon or pass priority to opponent.
2. Opponent may negate summon of monster.
3. Turn player may activate the effect of tour guide or pass priority to opponent.
4. Opponent may chain to the effect or activate an effect when priority is passed.
In this situation:
1. Not applied
2. Not applied
3. Activates effect
4. Activates trap hole
Result:
Tour guide goes to the grave and the effect resolves special summoning the second monster.
* Note once you pass priority you cannot get it back.
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When is priority used?
A: EVERYWHERE
Draw Phase
1. Turn player may activate a card effect or pass priority
2. Opponent may activate a card effect
Standby/Main 1/2 /End Phase
1. Turn player may activate a card effect or pass priority
2. Opponent may activate a card effect.
Battle Phase: - This is where it gets different
Turn Player declares an attack (with target selected)
1. Turn player may activate a card effect in responce to attack declaration or pass priority
2. Opponent may activate a card effect.
Damage Step:
1. Turn player may activate or pass priority
2. Opponent may activate an effect
End of Damage step (Where flip effects and graveyard effects activate)
1. Turn player may activate or pass priority
2. Opponent may activate an effect
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In short:
Priority is the mechanic that determines who will be allowed to activate a card effect first.