Crystalline Nautilus
{2}{U}
Enchantment Creature -- Nautilus
4/4
Bestow {3}{U}{U} (If you cast ~this~ for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
When ~this~ becomes the target of a spell or ability, sacrifice it.
Enchanted creature gets +4/+4 and has "When ~this~ becomes the target of a spell or ability, sacrifice it."
Makeshift Mannequin
{3}{B}
Instant
Return target creature card from your graveyard to the battlefield with a mannequin counter on it. For as long as that creature has a mannequin counter on it, it has "When ~this~ becomes the target of a spell or ability, sacrifice it."
Phantasmal Image
{1}{U}
Creature -- Illusion
0/0
You may have ~this~ enter as a copy of any creature on the battlefield, except it's an Illusion in addition to its other types and it has "When ~this~ becomes the target of a spell or ability, sacrifice it."