anyone explain the value of a stat decrease on an attack card?

unless i'm mistaken, you are only allowed one attack per turn, so for example lets say you attack with rip tide using a water attack critter, it deals the 10 damage and lowers the opponents courage by 25 till the end of the turn............well now, if you could follow it with a second attack that has a challenge using courage that would make sense, but that doesn't seem to be the case, and maybe i'm missing something, but to me it seems you would do the damage, maybe follow up with a mugic but it doesn't look (so far) that those have challenges on them and then the effect would end when you end your turn........so where is the advantage to that?.................unless it means that the skill decrease remains for both players turns, but it doesn't sound like that either..............anyways.........any insight is appreciated, thanks.