Summon Illusion is a monsters-only spell which temporarily creates a hostile exact duplicate of the target (usually your character) as a non-undead version of a player ghost. This clone will eventually dissipate on its own, but will be armed with all of your equipment and spells until then, making it extraordinarily dangerous. It is vulnerable to Abjuration, thankfully.
The following enemies cast Summon Illusion:
- R Mara