The spell doesn't specify your army, so you can create guys in your oposing army with it? If so since it creates presence you can just make these even if he doesn't have any personalities there?
Creating Personalities with Essence of Gaki-Do
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
The spell doesn't specify your army, so you can create guys in your oposing army with it?
No. The created Spirit Personalities enter play on your side at the current battlefield.
Glossary, Battlefield: "Effects that [...] create units at, a battlefield normally put the units into the unit’s controller’s own side and army there."