So the effect its just on one dice result!? Well I don't see the hidden force, can you explain me please?
If i use FoC on a unit os Saurus Warriors for exemple, i can modify just one dice attack of all attack they made....thats correct?
Yes.
I'll try to explain its usefulness.
First of all' remember that the +1 will affect a dice after you see the roll, so when you use it, it will always turn a failed roll into a success.
Cast CoF on a stegadon.
Hero phase: use the +1 to modify the teleport or to increase the extra move granted by skink Alpha.
Shooting: it's always nice to hit with the giant bow.
Charge: +1 to charge can make the difference
Combat: a success with an attacks or a save.
And this will work also in the opponent turn:
Shooting: turn a failed save into a success
Combat: same as above.
Basically, you have a potential of 6 failed rolls, turned into a win. Even if you use it only half of the time, a spell that grants 3 positive results in a round is no joke.
Now imagine it on a EotG, when you roll for the effects of the engine (plus all the bonuses you may need in the other phases).
Or on a Knights unit, when you can turn a 5 into a 6 for mortal wounds.
Or on a Carnosaur (Yes, it will affect also the contest by the bloodroar)