The challenge: keeping Astarion in his sight while simultaneously avoiding an incoming knife.

It's almost successful. The knife catches him along the left side as Ellis dodges back, that movement the only reason he ends up with a shallow slice rather than a deep gash. Fighting bare-handed is not one of Ellis' primary skills, but it is a skill. And it's sufficient to avoid felling this man while still doling out some retribution.

Ducking beneath the second strike, he lands three heavy blows to the ribs. It's only partly meant to maneuver him in such a way so as Ellis can have both him and Astarion directly in his sight.

If it means this man's back is now to the greater threat in this altercation, well. Unfortunate for him.