Sarkhan Vol is a planeswalker who's effects need loyalty counters to use. The number of loyalty counters also means how much damage he can take before he is destroyed. You cannot have more than one Sarkhan Vol on the field at once. Planeswalkers can only be targeted as you would a creature. Planeswalkers can only be targeted as you would a creature, however this card isn't destroyed by world affects from cards like Wrath of God or Mass Calcify.
Sarkhan is a pretty over looked planeswalker mainly because his abilities are not as "good" as some of the others, however he can do a lot. His first ability can fit nicely into cards that are heavy hitters, yet don't have haste. His 2nd ability is very good too. Not only can you take your opponents creatures, but you can take your own and untap them. It can help you take a big creature with both high power and toughness and use it to not only attack, but also block. His last ability allows you to put 5 4/4 Red dragons with flying into play, which adds up to a total of 20 damage! If you can give them haste, and your opponent hasn't got any creatures that have/can block flying and hasn't gained any life, it's game over for them!