A Titanic Holy Sword wielded by Ultiel, its colored Black and Purple, has spikes on the blade part and on the handle, it looks deadly enough to give a slight concussion to someone.
"The ThistleBlade was made to rip apart the flesh, but in doing so requires immense strength just to hold. This sword was made for a giant's hands." - ThistleBlade Tool Tip
The Titanic ThistleBlade deals 425 PPH, the Weapon also has a GUI text, saying "The weight of Thistleblade was not meant for human hands. Your rolling is disabled" due to this, that means you CANNOT roll with the weapon, which is quite a huge downside.
To obtain the weapon, you must kill Ultiel.