Nowaru

Well, alright, but there's no need to linger in spots observed by multiple enemies simultaneously. She could even be positioned to the left of the upper-left corner of the map, and from there, in one turn while invisible, she could reach the desired location (she has a speed of around 30, right?). Then, she casts a spell on level 5, level 4, and the target, possibly on Ivory (although hopefully, he'll be far away), and that's it...
She could attack with a bow, perhaps. Or pre-emptively use a potion for AGI. Or both. Then there should be even fewer problems... The bow is to attack from a greater distance and reduce the chance of Ivory detecting her.