Catastor Again

To make it more clear, it's nt like Catastor can't activate its effect.
Here's how it goes:

The effect or “Ally of Justice Catastor” activates at the very start of the Damage Step before face-down monsters are flipped face-up.
At first, AOJ attacks a face down monster. At the very start of the Damage Step, AOJ's effect activates BEFORE the face-down monster is flipped face-up.

If “Ally of Justice Catastor” or the opponent’s monster is face-down at the start of the Damage Step, the effect of “Ally of Justice Catastor” will not apply.
Then, AOJ's effect will not apply since the face-down monster's Attribute is UNKNOWN at the very start of Damage Step coz the monster's face-down. So the effect doesn't met the requirement and can't be applied to the face-down monster.
Then damage calculation it's flipped up and so on~

Clear?

Next one,
"Ally of Justice Catastor"'s effect will activate when it battles a monster with multiple Attributes, such as "Dark Simorgh" or "Light and Darkness Dragon" - assuming that "Light and Darkness Dragon" doesn't negate the effect.

Clear?

Done

end./.