Pokemon Black and White Walkthrough Part 13: Pinwheel Forest (part 2)

Step 5: Battle Team Plasma as you go to the forest
Burgh will ask you to go west to look for Team Plasma when you enter the forest, while he heads north. Battle all the Grunts you see.

Step 6: Get the Dragon Skull back from Team Plasma
When you reach the end of the trail of Grunts, you will fight a Grunt who, after you deafet him, will give you the Dragon Skull.

Step 7: Meet Gorm
Right after the Grunt one of Team Plasma's seven Sages, Gorm, will come up. He leaves after you talk to him and so does Burgh, after telling you he will be waiting at the Castelia City Gym. As thanks for retreiving the Dragon Skull, Lenora will give you a Moon Stone.

Step 8: Head north on the Skyarrow Bride
After battling the trainers on the road (School Kid Sammy, Lass Eva, School Kid Millie), go north to the Skyarrow Bridge.

After capturring Cobalion                                                       

Step 9: Capture Virizion!
After capturing Cobalion in Mistralton Cave, you can proceed to the Rumination Field, where you will find Virizion.

Capture Virizion! Allrighty than, time to capture a ledgendary Pokemon! Virizion is a Lv. 42 Grass and Fighting type with the ability of Justified. It's moveset is Helping Hand, Retaliate, Giga Drain, and it's singature move Sacred Sword. For strategy you should first use supereffective move types like Fire, Ice, Poison, and Psychic. Than slowely lower it's hp down with Water, Grass, Electric, and Ground type moves. It's ability Justified makes it so that if you use a Dark type move against it, it's attack will go up.

Skyarrow Bridge field moves needed: none

Items
  Quick Claw

Step 1: Get the Quick Claw from a hiker in the gate leading to the bridge.

That was a boring bridge.