You are a devoted follower of the Lord of Blades, and your faith has been rewarded. Activate this ability to attempt to become a juggernaut of destruction for 24 seconds plus 6 seconds per Religious Lore feat you have.
While transformed, you have a +4 Profane bonus to Strength, +4 natural armor bonus to AC, a +4 profane bonus on damage rolls, +10 enhancement bonus to Will saves against mind affecting magic, and proficiency in all simple and martial weapons. Your base attack bonus equals your level. You lose your spellcasting ability. You have immunity to critical hits and sneak attacks, but cannot be healed by healing spells.
Testing: Using the ability does not actually seem to prohibit spellcasting. Best guess is that text is a leftover from the Tensor's spell, or it's description, that has since been removed from Bladesworn Transformation, but left the description unchanged.