Can someone tell me how to use raise spectre for blade vortex?

For the first time I want to see start a bv build, however I don't get the minion pact and spectre relation. Could you explain it as if you were explaining it to an idiot?

Should I choose a specific corpse or just a random one?

Should I raise that spectre every map?

How can I raise spectre If there were no corpses?

- there are specific monsters that have way higher max life pools than others, so they are the ideal choice for raise spectre, since minion pact is life-based, apparently these monsters are dark marionette (auto revives) or unholy aberration (from unholy trinity map boss fight)
- you raise the spectre every map, use minion pact on it, and cast blade vortex before the minion pact buff expires
- this "snapshots" the minion pact buff onto blade vortex as long as you keep up vortex stacks throughout the map
- not sure about the details for raising the spectre in a map, i'd assume desecrate but I don't see it in the build guide (gladiator version) linked below

https://www.youtube.com/watch?v=wvsQ6NVFibA