can the viper attack (opponent control more char ) when it affected by TBC?

Yes. The Black Cells prevents a character from changing its status from standing to kneeling, and vice versa. Normally, that stops a character from attacking since changing its status from standing to kneeling is a requirement of being declared as an attacker or defender. However, if you take away that requirement (with "does not kneel to..." text), then the limit from Black Cells does not make it impossible to be declared anymore. So long as the Viper is standing when he would be declared, his "does not kneel..." text will bypass the practical stop Black Cells would otherwise place on his ability to be declared as an attacker.

If the Red Viper(or any character that is at the moment with the status "does not kneel to attack") is knelt at some point, can he be declared as an attacker while being knelt? The cost to declare the character as an attacker is to kneel the character normally, but if that cost is no longer needed, then wouldn't "does not kneel to attack" also mean that the character doesn't have to be standing? Or is standing normally a requirement for declaring attackers?

Bomb said:

Indeed it is. From the rule book: "Already kneeling characters may not be declared as attackers."

Thanks Saturnine. That is what I thought I knew. It would make those "does not kneel to attack" effects a bit too strong.

Though there are "can attack/defend while knelt" effects in Lannister.

Khudzlin said:

Yes, those kind of abilities would, of course, "trump" the rule book.