What is the order of the factors to make a mutation? (ex. Element, atk, hp, etc.)
I'm not entirely sure what you mean here.
When the Mutation skill is cast, it is first checked whether the creature should die. It is then checked whether to turn in into an Abomination. If neither of these happens, it turns into a random non-upgraded creature with status 'mutation'. If the Improved Mutation skill is cast, it naturally 'skips' the first two steps.
When a creature with the status 'mutation' comes into play, it first receives a random skill. It then receives a random def boost, then a random ATK boost. It then picks a skill cost.
how does the game RNG work? (i.e. : which is the algorhytm that lies behind the RNG)
The RNG is Actionscript's Math.random() function. It returns a pseudo-random number n, where 0 <= n < 1.
Is the random pet selection mechanic the same as Fate Egg's?
And is SoSe using the Oracle card engine?
The same creature list is used for pets and Fate Eggs, but the probabilities are drastically different (Fate Egg has the same for all, see here (
http://elementscommunity.org/forum/index.php/topic,32442.msg447747#msg447747) for pets).
SoSe uses the Oracle card list, but not the engine (the Oracle card engine has a chance to give a nymph).