The Royal Griffin is a sub-species of the common griffin. It is the first serious monster that you will fight in The Witcher 3: Wild Hunt. One and likely only difference from their relative is size of them, they are bigger with longer wings.
As stated earlier, its a first true beast that you encounter in game with Vesemir at White Orchard on contract by Peter Saar Gwynleve in exchange for a pouch of gold and info about Yennefer of Vengerberg.
For strategies, see Griffin (creature).