[quote=@Fabulous Knight]
<Snipped quote by Lugubrious>

Does this also give them sentience? --If not, what [i]are[/i] the effects?
[/quote]

Not necessarily.  It's more along the lines of accidentally putting something where it doesn't belong.  Sentience means new souls are created.  Slough's thing uses existing souls.  If the soul had sentience in its past life, maybe, but the reincarnation process affects the soul itself, as well.