The pet you will obtain will probably be the Reward of [Event] Cherry Blossom, Lucky Coin, Devil Square, Skeleton King, Selupan, White Wizzard. They normally drop out from bosses and other mobs while playing.
Thease pets is good for obtaining AddHP, AddMP, DmgRat, AttSpd, DoubleDmgRate, TripleDmgRate, AddExp, DoubleDamageResist, DefResistIgnore, SDResIgnore, ResCritDmg, ResExcDmg, BlockStuck, Ref and of course for PVP. You can also make them immortal, by upgrading pets with some kind of armor.