A: Spider of Morlat was in play as permanent event (Player 1)
B: (Player 2) moves his company through Southern Mirkwood -> as a result, the company is attacked by the Spider of the Morlat
C: (Player 2) plays Marvels Told to remove the Spider of the Morlat
D: (Player 1) counters with Black Vapour.
As from my perception, Black Vapour is a valid counter to Marvels Told, since it has a effect that would cancel a spider attack (the automatic attack of the Spider of the Morlat)Wording of Black Vapour: Target any effect (declared earlier in the same chain of effects) that would cancel a spider attack. Make a roll and add the attack's prowess. If the result is greater than 14, the effect is canceled and the attack receives +1 prowess.
Alternatively, +1 prowess to a spider attack.
This card may be revealed as an on-guard card for either effect.
In our tournament, we could not reach a decision and threw a die to resolve the case, but we are curious to know, what the official resolution would be.