How do you consistently have your shade attack with vengeful spirit?

[Shame]

Trying to replicate this:
https://www.youtube.com/watch?v=tXSKuiqNb_4

So far, after attacking several dozen times, the shade has only either cast it off-screen above me before even reaching the bottom or cast it at the top of where it spawns only one time, as I was messing around with trying to dodge it to see if there is any pattern in doing so. Any ideas how to make this consistent or is it really almost entirely rng based with low % chance that it happens and you just have to keep bringing it down to the area?

[Perseus]

Here's what i know from all the shade skips i've done :
-Your shade has a limited amount of spells it can cast : 1 + (1*every additional soul vessel you had when you died). To refill those, you can simply leave the room and come back.

-Before casting vengeful spirit, your shade will try to back up and attempt to match your height.

-I don't know any patterns that determine when the shade decides to cast.

You'll probably have to keep bringing your shade down, but more soul vessels will make it more consistent whether your shade still has enough spell charges left by the time it gets down.