[Karel]

So apparently, I was told that if you're a blood mage and you summon a blood spirit and Give it the Endowment power... or if you channel it and use its abilities

you can get the Essence Drain, and so you can just... drain essence and get yourself augmented with Bioware or even Cyberware... essentially at no essence cost?

I got into a bit of an argument cause... well, it's incredibly abusable, so I wan't to know if this is legit possible

Is this how it works? no? possibly any official response from an errata mod?

[Michael Chandra]

Sounds like too extreme a situation for anyone to consider but I'd say there's two things blocking this.
First, your magic is connected not to essence but to essence loss unless you're Infected. So a GM can easily argue you still lose the Magic immediately.

Alternatively, using Essence Drain obviously makes you an entity that loses Essence. So you now lose Magic if your Essence ever drops below 6 again.

Anyway since you need permission to Blood Mage honestly I'd just smack this down as GM. Any player intending to abuse a loophole like this without acknowledging that the GM can spot it as it is and block it, likely cannot be trusted to not make a scene when something doesn't go their way.

[Cabral]

I don't see how to give a blood spirit endowment, even as a free spirit. If channeling the spirit, when using the spirit powers, I would argue that the spirit receives the Essence or the magician starts losing 1 Essence per day.

To supplement Michael's point about magic loss being tied to Essence loss, not current Essence value, the Essence Drain power doesn't increase the maximum Essence so even if the character could benefit from the essence gain, he would start at 6, gain 1 to still be at 6, lose 1 to the implant, dropping to 5 essence and a maximum 5 magic. Draining 1 again may take him up to 6 essence, but leaves his magic and maximum magic unchanged.