master pet is the lowest pet rating, or was untill the last upgrade, now the pet rating starts with ELDER which is the normal pets ( tree baby & walking fox) & the higher rated pets r mythical then legendary ones.
yeah and you must used phase ball's to phase your pet's. elder and mythic pet phase ball is available in your guild icon and you can buy that for 5 credits eachother pet phase balls are in shop but it cost ingots.