Mythic rare magic the gathering cards? How do they work?

What you have there is known as a Planeswalker.

Planeswalkers are permanents that have multiple abilities that you can use. In the bottom right corner is a number, that is the number of loyalty counters (basically their life) that they start off with. Once it hits zero, the planeswalker is removed from the battlefield.

You can only activate one of the planeswalker's abilities once per turn, and only when you can activate a sorcery. The +/- number next to the ability is the "cost" that will affect a planeswalker's loyalty. In "Garruk, Primal Hunter", for example, if you activated his +1 ability, you would increase his loyalty by one (so it would be 4, assuming he was at 3 initially), and you would get a 3/3 beast token. Or, if you used his -3 ability, you would reduce his loyalty by three (so it would be 0, assuming he was at 3 initially, which means he'll be removed from the battlefield), and you would draw cards equal to the highest power of your creatures.

Also, when your opponent attacks you, he can choose to either attack you or your planeswalker. You can choose to block creatures attacking your planesalker, but when your opponent declares his attackers, he'll have to mention if they are going to be swinging at you or your planeswalker. He can declare some, all, or none of his creatures to the planeswalker. If the planeswalker takes damage this way, he'll lose loyalty equal to the damage. So if your opponent two 2/2s attacking Garruk, and you can only block one of them, Garruk would have to reduce his loyalty by 2.

Another thing is when a spell that targets a player resolves. So, let's say your opponent casts Lightning Bolt, targeting you for three damage. During resolution, your opponent can redirect that three damage to Garruk, making him take the damage instead, which will reduce his loyalty by 3. The reason for this redirection is because Planeswalkers are neither creatures nor players. Anything that targets or affects creatures WILL NOT affect Planeswalkers (unless they were turned into creatures, but I digress). Anything targeting players maybe redirected to them, but cannot directly affect them (basically saying that if you hexproof yourself, you've pretty much made them immune to targeted burn damage).

Also, Planeswalkers have their own sort of legend rule. There can only be one Planeswalker of a given subtype at a time. This means, if you had Garruk, Primal Hunter on the field, if another Garruk enters the battlefield, both Garruks will be sent to the graveyard.

This type of card is called a Planeswalker. These are special cards with great abilities (usually). They work on loyalty counters. Check this website out for more tips

https://www.wizards.com/Magic/TCG/Article.aspx?x=m...

This is from the people who make and distribute the game, couldn't think of a better source for current rules on this card type. Though this is a very powerful card and usually targeted fast. Here is a forum discussing the particular one you are looking at

http://forums.mtgsalvation.com/showthread.php?t=33...