Pegasus' Creator skill is one of the skill to be updated during the upcoming rebalancing, changing the cards which you can get from the skill. A recent leak shows an updated list of cards you can draw with the skill.
Can be used if your Life Points drop below 2000. In the Draw Phase, instead of doing a normal draw, a powerful card, from outside of your Deck, is added to your hand. This skill can only be used once per Duel.
Some guy in reddit posted: it is not random. The game algorithm will take into account your cards in hand, LP compared to opponent etc. Then they will give you one of the card based on situation. However that was before skill update. I believe mechanism now is still the same, just different card added into your hand.