Evard's Black Tentacles 3.5

[Chester]

So, I was wondering about the wording for Evard's Black Tentacles.

Normally, on my opponent's turn, he/she can use a move action to attempt to break free of the grapple (assuming he's caught in the tentacles).

Also, on MY turn, I must make another grapple check to see if the tentacles do 1d6+4 points of damage to grappled opponents. However, if my opponents pass this particular grapple check, do they a) break free of the grapple, or b) remain grappled but take no damage.

This is currently a source of debate with my group!

[Khedrac]

On the caster's turn there is an opposed grapple check to deal/avoid the listed damage - the affected do not have a chance to break free on this check.

On the affected creature's turn they can choose to attempt to break free following the normal grapple rules. No damage is inflicted if they try and fail (or fail to try). Attempting to break a grapple is a weird action type - essentially the same as an attack.
it is not a move action - a single attempt is a standard action, but multiple attempts can be made (as many as one has iterative attacks) as a full-round action (each subsequent attempt suffering a cumulative -5 penalty, as per iterative attacks). Again, like attacks, one does not have to choose to make the full-round action until after one knows the result of the first attempt.

Remember that a creature that breaks free is not re-grappled if they remain in the area of effect - only creatures entering the area are subject to new grapple attempts after the initial casting.