Getting in that drink of water from Aquamenti will keep you from dehydrating but it won't won't help you keep safe from the Runespoor.

The loose of your armor might not be the best thing for you but it serves you well in giving you the focus needed in casting that jelly brain jinx again. This time it works, the left head falling into a daze like fog.

With both the middle and left heads confused and in a dreamlike state, the right head stares straight at you baring it's fangs and hissing, however unable to come after you. How long can you keep both charms going before the Runespoor breaks it's from it's haze?

Using Oppugno on that rock works well for you and the right head bares it's fangs hissing loudly at the dog you created.

When you crawl to the door you're able to make out the second line of runes which reads:

ᛋᚢᛒᛞᚢ ᚦ ᛒᛖᛋᛏ ᛁᚾ ᚾᚨᛏᚱ ᛏᛟ ᛗᚨᚲ ᛁᛏ ᛟᛈᚾ ᚠᛟᚱ ᚦᛖ

Hopefully you can figure it out quickly enough...