A couple questions about the Trickery Cleric ability.

1. I had a player's duplicate be in the area of a fireball. What would happen? Would it do anything to the clone? 

2. Can a duplicate be the target of a touch spell? If not, what about any other spells?

1) The duplicate is intangible, so there is nothing there for the fireball to hurt. The fire would pass right through it.

2) The duplicate could be targeted by a touch spell likeInflict Wounds or Shocking Grasp, the casting would not affect it, but it's intangible nature would reveal it do be a duplicate when the monsters touch goes right through it.

Broadly speaking, since the duplicate is not a creature, spells and other effects that say things like "each creature in a 20-foot radius" do not affect it.

I notice that the 2024 version says that it "mimics your expressions and gestures". I think one consequence of this is that if both you and the duplicate were in the affected area of a spell like Fireball, it would look like both you and the duplicate were affected by it, because any visible reaction you made to the damage (reeling back in pain, your hair getting singed, etc.) would be done by the duplicate as well. But the duplicate still wouldn't actually be affected.

Regarding 2, I don't think it can be the target of anything that does not target a magical effect. Nothing about Invoke Duplicity says that the effect creates a creature or object. Touch spells will not generally affect it, but Dispel Magic will.

Quote from SmiteMakesRight_3_5 >>

Regarding 2, I don't think it can be the target of anything that does not target a magical effect. Nothing about Invoke Duplicity says that the effect creates a creature or object. Touch spells will not generally affect it, but Dispel Magic will.

 I agree with you.

Also, if it's helpful for the OP or someone in the future: 5e Trickery Domain Cleric Question - Rules & Game Mechanics

Quote from SmiteMakesRight_3_5 >>

Regarding 2, I don't think it can be the target of anything that does not target a magical effect. Nothing about Invoke Duplicity says that the effect creates a creature or object. Touch spells will not generally affect it, but Dispel Magic will.

It does raise the question of, if someone tried to cast something like Inflict Wounds on it, thinking it was a real creature, would it still use up the spell slot? Would it still use up the action?

Quote from wagnarokkr >>

Quote from SmiteMakesRight_3_5 >>

Regarding 2, I don't think it can be the target of anything that does not target a magical effect. Nothing about Invoke Duplicity says that the effect creates a creature or object. Touch spells will not generally affect it, but Dispel Magic will.

It does raise the question of, if someone tried to cast something like Inflict Wounds on it, thinking it was a real creature, would it still use up the spell slot? Would it still use up the action?

 I think in those cases we need to apply this rule:

Invalid Targets. If you cast a spell on someone or something that can’t be affected by it, nothing happens to that target, but if you used a spell slot to cast the spell, the slot is still expended.

If the spell normally has no effect on a target that succeeds on a saving throw, the invalid target appears to have succeeded on its saving throw, even though it didn’t attempt one (giving no hint that the creature is an invalid target). Otherwise, you perceive that the spell did nothing to the target.