Mission: "Stop her if you can" - How to tame Karnhell? - Achievement "Amber Ochre" - Dofus 2

Karnhell invokes a glyph, when she starts in the red squares of the glyph, a number appears above it, from 1 to 5 (in Roman numerals). Each time she starts her turn in the red glyph, this number increases. When the number above Karnhell reaches V, he casts a spell called "You can catch me!" and we, using at this moment the spell "Taming of mount", win the combat, automatically.
Caution: All the pj that begin in the glyph will have the Roman numeral; in V, kill.