OOC: Yes, true strike is an Su ability that activates on an attack, like a paladin's smite evil. So yes, B can.
As for Mystic, I thought I had to hold the spell for an extra standard action. My bad. I just looked up the rules. Oops.
Assuming from your map that the Blackcloaks 3&4 are against the wall alone, Mystic will cast
Evard's Black Tentacles to grapple them. If not, just use the enervation round I posted above.
[sblock=prepared spells]
(DC 17+ level):
0- detect magic (2), light, cure minor wounds,
1- bless, cure light wounds (2), snake's swiftness, silent image, charm person,
2- hold person, silence, mirror image, align fang, augury, align weapon
3- dispel magic, invisibility purge (2), haste, (1 used)
4- polymorph, divine power, enervation, flame strike, restoration,
5- raise dead, heal (2), summon monster V,
6-blade barrier, magic jar, mislead,
7-greater teleport, (1 used)
[/sblock]
IC: Mystic waves his hand. A field of tentacles, black as night but as unyielding as stone, slip like shadows over certain persons in black cloaks.
Grapple rolls:
1d20+21=22, 1d20+21=31, 1d20+21=34, 1d20+21=39, 1d20+21=22
Damage (if applicable):
1d6+4=10
Sorry about that.