FYI - This card is really messed up.
The Amalekites' Slave (RA)
Type: Evil Char. • Brigade: Gold/Brown • Ability: 4 / 4 • Class: None • Special Ability: If blocking, you may place this card in opponent's Land of Bondage to search your deck for a human Evil Character and add it to the battle. • Play As: If blocking, you may choose to have your opponent capture this card to search your deck for a human Evil Character and add to battle the Evil Character. • Identifiers: OT Male Human, Egypt • Verse: I Samuel 30:13
First, as originally written there's no indication it ever becomes a lost soul.
Second, the play-as gives your opponent the ability to search your deck.
Third, it is my belief that "lost soul cards" <> "cards treated as lost souls".
I agree with all of those points (maybe not the second one, but the wording is definitely poor enough for someone to come to that conclusion). The Play As should be rewritten, as your opponent is certainly not the one doing the capturing, you are. It's like Dungeon of Malchiah, I capture, and place in your LoB.
As to the third point, if a card said "place a Lost Soul card on your deck" then I would agree that you couldn't target a captured character. However, I don't know what that has to do with the question at hand. The question is whether or not captured characters retain their abilities. I agree that is something we should figure out; I will post about it on the other side of the boards.