Mana String on Sword

[Puffin]

The game keeps telling me to use mana string on a sword that is chained to the ground next to a chest I opened.

It's when I get transported to viewpoint isle without Karja and Grenn

Is it supposed to do something? Because when I press button, nothing happens.

[Rayne_2007]

The sword is a Mana String grapple point, it just creates a small short cut by-passing the need to climb up part of the path...

I believe it is also initially covered in vines, requiring use of Adol's Mana Burst (hold 'Attack' button briefly to charge) before it can be used as a grapple point.