I am going off topic, but could the artifact affect SH same way The Dark Urge works? I've never seen a vid of mad SH before, and it actually makes some sense. She literally says that 'there is so much blood everywhere' when mentions the whispers in her head. Sounds kinda Dark Urgy, no?
We don't have a full answer there but it is clear that either the artifact or possibly the goddess Shar herself(who initially sent Shadowheart on the suicide mission for the artifact) is extremely intent on the artifact ending with the player and if you keep denying Shadowheart there will be voices in her head not associated with the tadpole literally driving her mad to keep returning to your party and if you deny her she'll be driven to suicide by attacking your party at which point the artifact becomes magically attached to your character in a manner that you cannot get rid of it. So the bigger questions here are...was this all in Shar's design for the artifact? Just how closely involved is Shar with the party at the start of the game? Is Shar also the "guardian" in our dreams, driving us to embrace the tadpole, promising protection? Well...very possibly. It is the artifact she sent Shadowheart after that protects us from being controlled by the Absolute.