Maybe Karnas should be able to free himself from Tancred's hand and float around attacking enemies by himself and casting spells, kinda like a Mordenkainen's Magnificent Sword spell, but stronger, or maybe, you could make a Karnas NPC, who would be part of the party and able to memorise spells and float around beside Tancred, and then when Tancred needed to Butt-Kick for Justice Karnas could use a special ability that placed him in Tancred's hand so he could chop some foes to bits, it would be REALLY cool if Karnas the Sword could memorize spells while in Tancred's hand, so he could cast spells like a Sorcerer or something.
------------------
Worshipper of Tiax.
Wielder of the ancient Lawyer spells.
Member of the HADB clan.
Ally of the Fluffy Queen and the Dreaded Red Fluffy
General of the highest class and Leader of the Legal Department and Jumprope Compound in the IW Peacekeeping Force.
I've also got a pretty long sig.