If a monster is immune to a trait such as Fire, can a spell with the trait Fire still be used? The reason I ask is that Seoni ran into a monster with this trait but the only card she had in her hand was a Fire based attacked spell. Since she knew she would lose the fight she wanted to cast the spell just so she could recharge it rather than lose it to damage.
I was unsure of what the ruling would be. We decided she could play it and it simply did no damage to the monster and allowed her to recharge it.
It can't be played at all.
If the card you’re encountering states that it is immune to a particular trait, players may not play cards with the specified trait, use powers that would add that trait to the check, or roll dice with that trait during the encounter.
If a monster is immune to a trait such as Fire, can a spell with the trait Fire still be used? The reason I ask is that Seoni ran into a monster with this trait but the only card she had in her hand was a Fire based attacked spell. Since she knew she would lose the fight she wanted to cast the spell just so she could recharge it rather than lose it to damage.
Hawkmoon269 provided the accurate answer to your question. Coincidentally, though, I was about to create a new thread on this topic, since a similar (but slightly more complex) question was answered in another thread on a different forum. I'll post a truncated version here as well, since it's actually another example of the same rule :)
The original question on the other forum was:
Valeros fights a poison-immune monster. He hits it on the head with a Longsword. If he also has a Venomous Dagger +2, using its second power, he could recharge it to add 1d4+2 to the combat check, but that would also add the poison trait. Is that allowed?
Vic Wertz also referred to the same rulebook snippet mentioned by Hawkmoon269 when answering this case. For your Seoni example, the card would be invalid because the card had the fire trait. For the Valeros example, the card is valid since the Venomous Dagger +2 actually does not have the Poison trait. So the card can be played. However, that specific power would add the poison trait, so that power can't be played. Valeros can either use the base dagger attack (without any recharges that add Poison), or just stick to his Longsword.
And what if Ezren put down an Incendiary cloud earlier this turn and now he's fighting against a fire immune creature. Would pummeling it with a quarterstaff be useless due to the fire trait?
I'll let Vic do the talking on this one, since he phrased it very well:
In Ezren's case, the spell has already been played, and the immunity can't make you un-play the spell, so it does technically add 2d4 with the Fire trait to his check—but since you're not allowed to roll dice with that trait during the encounter, it doesn't matter.
And there we see an example of the third part of the rule: not rolling dice with the trait against a card that's immune to it.
Edit: Fixed a capital letter