I am in a discussion with a player about Ghost of the Rooftops assassin utility power. He thinks he can use that on ANY wall without doing an athletics check then each round hang onto that wall and attack with his sling. I let him know I would let him do some walls but there will be certain instances where he may need an athletics check. Also is there rules for attacking while hanging from a wall? The power seems to be a bit vague on what you can climb. For instance he wanted to use this while climbing a very crumbly wall while water is dripping down from the wall. I had him do a lowered athletics check.
Ghost of the Rooftops
Your skill at climbing and leaping allows you to move across the rooftops unhindered.
At-Will Martial Move Action Personal
Effect: You climb or make a long jump, moving a number of squares up to your speed, without making an Athletics check.
Special: You can use this power only once per round.
Thanks for any help or suggestions.