Combination of Apple of discord (chaos +4) and Agats soul cage (chaos +3) give to my barb total chaos skill of +3 !!!, to my HL +7 (ok) an to my paladin +11 !!!
E.g. When I add apple of discord to the barb , it shows basic chaos skill -4 then modified by artefact +4 giving chaos skill of zero . That wrong basic chaos skill -4 is not visible until the artefact (either apple or soul cage) is added to the barb. It works the same for paladin but he gets the basic chaos +4 therefore he receives +11 in total.
It seems that the incorrect chaos skill is applied in battles too ....or at least it is displayed on battle reports.
Game ID : 58787
Thanks for looking into this / explanation