Skill Sequence is, yet again, sorted by your role. First I'll explain the actual skills:

Passive: Chosen of the Storm



Heals volibear for 30% of his Maximum Health over 6 seconds when he drops below 30% Health.



120 second cooldown



Explanation:

A pretty good passive IMO, its kind of like a mini Mundo ulti, and can bait someone into a turret dive that they don't have the dmg to pull through on,(unless they have ignite/grievous wounds)



Rolling Thunder

Volibear gains 45% Movement Speed while moving toward enemy champions. Lasts 4 seconds.



Volibear's next attack deals an additional 25 / 50 / 75 / 100 / 125 physical damage and flings the target behind him.



12/11/10/9/8 second Cooldown



Costs 40 Mana



Explanation:

This is similar to singed's fling, and can be used for ganking and initiating, you can force a fight with it or force someone to flash away. at level 1 the bonus movement speed is greater then ghost.



Frenzy:

Passive: Volibear gains 8% Attack Speed with each attack. Stacks up to 3 times.



Active: When Volibear has (3) stacks of Frenzy, he can bite an enemy to deal (90/140/190/240/290) (+20% of bonus Health) physical damage, increased by (1)% for each (1)% health the target is missing.



Cooldown 18 Seconds



Cost 35 Mana



Explanation:

Frenzy gives Volibear a passive-like skill that, when it reaches max stacks (3), makes you able too hit an enemy once, for a great amount of damage. The stacks are lost over time, but, which this build rebuilding your stacks isn't any problem.



Majestic Roar:

Volibear deals (60/95/130/165/200) (+60% of ability power) magic damage to nearby enemies and slow them by 30% for 3 seconds.



Cooldown 11 Seconds



Cost 60 / 65 / 70 / 75 / 80 mana



Explanation:

Majestic Roar basically is an AOE slow against all kind of enemies, and it fears minions and monsters. Very usefull too initiate or too slow your enemies down. Being in a 1v1 fight with minions can give you an advantage as well, since you can fear the minions stopping them from attacking you.



Thunder Claws:

Volibear channels the storm, causing all basic attacks for (12) seconds to deal (75/115/155) (+30% of ability power) magic damage, which chains to 4 nearby enemies.



Cost 100 Mana



Cooldown 100 / 90 / 80 seconds