No, Horus LV6 is not a valid choice and can never be chosen to take part in Creature Swap's effect.miiaah said:Horus isn't an invalid target. He can be targeted if he is the last monster of the field (see the rulings). He's just unaffected by the effect.
Truthfully, even if it was targeted, you still could not target Horus LV6 with a Spell Card if he is the only monster you control. You have to have the ability to resolve an effect before you activate it.miiaah said:Sorry, I forgot Creature Swap does not target.