User blog comment:NyricTheDeceiver/The Perfect Army/@comment-30247117-20150819212514/@comment-4867780-20150819225452

Past Manipulation seems to be a remnant of Meta Summoning's previous version (background part of "Meta Character Creation"), though it still has some ground in that you can decide on the entity's origin and what was its life up to this point ("drawing" it from the ocean of possibilities - Meta Probability style - rather thant outright creating it).

On the other hand, since the person that you are is already determined (singular and pre-existing), the entity's past cannot be interwined with yours (though it may include any pre-summon circumstance explaining how it eventually entered your service).