Deekah triggers, creating a 0/0 Fractal creature token that enters with a +1/+1 counter on it.
Resolve Essence Flux, blinking Skullwinder.
Skullwinder enters the battlefield, returning Essence Flux from your graveyard to your hand and causing target opponent to return a card from their graveyard to their hand.
Activate Phyrexian Altar by sacrificing the Fractal, adding ({U} magic symbol) .