fabian771, you already answered your own question.
Question:
HOW HARD IS IT TO GET THE CARD?!
Answer:
And for getting them I know you only can get them from oracle.
This section of the forum is for posting and discussing decks that you place in the Arena, using the card given to you by the Oracle on that day. That is exactly what this deck was.
you must have gotten a blue nymph from oracle and added the one you won
Exactly right. That is exactly how I built this deck. Today, six months later, I still have only one Blue Nymph, and only six total. Sometimes, I wait for months. Once, I waited only two days between Nymphs. It happens, when it happens. Apologies; there simply is no other answer.