Deekah triggers, creating a 0/0 Fractal creature token that enters with a +1/+1 counter on it.
Resolve Cloudshift, blinking Skullwinder.
Skullwinder enters the battlefield, returning Cloudshift 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 ({W} magic symbol) .
Repeat.
Results
Infinite death triggers.
Infinite ETB.
Infinite LTB.
Infinite magecraft triggers.
Infinite sacrifice triggers.
Infinite storm count.
Target opponent returns all cards in their graveyard to their hand.