Ishya_Chan
Its a Turtle so let the sword have some offense with Ice or Water. To Freeze when slashed or augmented water pressure slash (Like a high pressured water cutter) that has longer range and can integrate with Sword Intent for more piercing destruction. The scabbard could have like a Self Healing Breathing, or increased Defense for his body and toughness for the scabbard to be used as a blunt melee tool for offense or defense. The Sword to kill, The Scabbard to Bludgeon or block.