Frozen Moat says: Kneel it when a character is attacking you and that character's textbox is treated as blank until the end of the phase.

Scenario: Opponent running Martell has fewer characters than me (Stark), so his Red Viper doesn't kneel to attack. Then, he declares Red Viper as attacker, and after that there is an action window where I kneel Frozen Moat to remove RV's textbox.

Question: Does this mean the first challenge RV doesn't kneel to attack and after his textbox is blank, he must kneel to initiate the second challenge? Or, maybe my usage of Frozen Moat is wrong?

The blanking effect of Frozen Moat lasts only until the end of the challenge, not the end of the phase as you stated. So by the time your opponent has the opportunity to declare a second challenge, the Red Viper is not blanked and therefore doesn't kneel in your scenario.

ktei2008 said:

Re-read Frozen Moat. It blanks one attacking character's textbox until the end of the challenge, not until the end of the phase. So, in the first attack TRV is already attacking when FM hits, and by the time he's declared as an attacker again, FM has stopped working. In short, FM doesn't help you with the doesn't-kneel-to-attack-thing. Still it might be worth it to blank TRV with FM. He loses Renown, and he loses his immunities, making him susceptible to all kinds of nasty stuff. Lethal Counterattck anyone? Routing the Charge?

Yeah, I re-read it. It is stated 'until the of the challenge', not 'the phase'. You guys are right. ****... We played all wrong. RV is too powerful...