The book makes no distinction between Maneuvers (for movement) and Magic Maneuvers. So would using a net, hamstring, or ice attack, and adding the ensnare trait prevent a caster from using 'maneuvers' for concentrate? Effectively un-summoning barriers/minions etc?

No. Using a maneuver is not doing a maneuver.

As far as I'm concerned, the immobilized condition prevents characters from performing maneuvers, so they would not be able to concentrate on their following turns. However, immobilization doesn't nullify previously performed maneuvers, so ensnaring would not instantly unsummon a minion, just as it wouldn't drag a character out of cover if he previously used a maneuver to hide behind it.

Whilst you can not perform the concentrate manoeuvre (or any manoeuvre for that matter) you can perform actions. One action they can perform is a Hard Athletics check to break out of the ensnare. Generally magic is harder, so for a Daunting Difficulty I would allow the player to attempt to use magic to break the bonds instead.

If the Ensnare is of magical origin then they could also use the Dispel spell (with setbacks for bound hands!) to try and remove the effect (I would even allow this against an Attack Spell that used the Ice effect)

Then lastly I would perhaps consider allowing them to make a Hard Discipline check as an Action to gain the benefits of the Concentrate manoeuvre

Extra bit: the way I try to think about Ensnare is the distraction it is for you. You are not just tied up, your panicking, some crazy guy just threw a net over you and now they are drawing a sword, not an easy time to concentrate.

On 10/12/2018 at 5:49 AM, Klort said:

As far as I'm concerned, the immobilized condition prevents characters from performing maneuvers, so they would not be able to concentrate on their following turns. However, immobilization doesn't nullify previously performed maneuvers, so ensnaring would not instantly unsummon a minion, just as it wouldn't drag a character out of cover if he previously used a maneuver to hide behind it.

True, but as per the rules summons act immediately after the casters turn, and concentrate allows the spell to continue to the end of the players next turn, so unless they are able to break the ensnare, the summons will not be able to act before being removed.

Immobilized says that the character cannot perform maneuvers. Concentration is a maneuver. So, just like an Ensnared character cannot aim or manage gear, they cannot concentrate. It does not shutdown a caster, but certainly makes things difficult for them just like all other characters. This is probably on purpose. So rather than the caster just completely ignoring a status effect they must deal with it just like everyone else. The concentration maneuver maintains a spell's effect for one additional round until the end of the character's next turn. Actions and maneuvers can be performed in any order. So the caster is able to deal with this problem by spending their action to do whatever is appropriate. If that is successful, they can get expend a maneuver to extend their spell, if not then the spell's effect will end at the end of the caster's turn. If they choose not to deal with the Ensnare they could instead cast their concentration spell again. The previous one will stop at the end of the current turn and the new one will stay active until the caster's next turn.