The Myth and Legends skill is a special skill that no class gets. It is used to tame mythical monsters such as Unicorns.
Unlike the other taming skills this skill comes entirely from item bonuses, there is no way to train this skill.
Mythical monsters are very rare and hard to come by in general.
Skill Use
To enslave a mythical monster you must first find one there are no tracking skills for mythical monsters so finding one depends entirely on luck.
When you move the mouse over a monster it will tell you its classification in the middle of the screen so it is fairly simple to spot mythical monsters it will also list how much skill and what skill is needed to tame this particular monster.
If you have enough skill simply click the button marked Control in the middle bank of buttons after selecting the monster. This will tame the pet and make it available to you on the Minions > Manage screen, you will gain some experience for taming.
By default you have a total of 4 pet slots, this is broken down as 1 pet in stables and 3 pets out of stables. You can purchase additional pet slots via the File > Buy Extras > Enhancements screen.
Formula
Skill required = (Monster Level * 5)
i.e. To tame a level 100 monster you need 500 skill.