#377 Regirock - Regirock is found in the Underground Ruins, deep under Clay Path. There is a complicated puzzle before getting to it. The puzzle requires you to move 6 steps down from the centerpiece and then move 9 steps right. Then select down to hit a hidden switch. Regirock is available then. It's at Level 65
#378 Regice [Technically White exclusive] - Regice can only be obtained after Regirock has been caught. After Regirock's capture you will gain the Iceberg key which is exclusive to White 2. Once you have this item you will be able to find Regice in the same place you found Regirock. It's at Level 65
#379 Registeel [Technically Black exclusive] - Registeel is the same case as Regice. In Black 2 after capturing Regirock you will obtain the Steel key. It's found in the same place as the other golems. These two keys are transferable by Unova Link. It's at Level 65
#486 Regigigas - Bring all 3 Regi's with you to the basement of Twist Mountain. Regigigas will then awaken and will battle you. It's all Level 68
#381 Latios [Black 2 exclusive] - After defeating the Elite 4 the dreamyard becomes accessible. Once you enter you will be greeted by Latios. It will fly off around the yard and you'll have to chase it. Once found a few times it will challenge you. He's at Level 68
#380 Latias [White 2 exclusive] - Exactly the same case as Latios.
After defeating the Elite 4, visit the Heart Cave where Juniper and the player will meet the Pixies, they will fly off to various places around Unova.
#480 Uxie - Waiting outside Nacrene City Museum. It's at Level 65.
#481 Mesprit - At the summit of Celestial Tower. It's at Level 65. You need to be standing on a particular spot.
#482 Azelf - TBA. It's at Level 65
Heatran and Cresselia are two other legends that appear in BW2 that aren't Unova-native.
#485 Heatran - Once the Magma Stone has been retrieved from Route 18. Go back to Rebirth Mountain and into Rebirth Cave where Bianca spoke about Heatran previously. Heatran will appear at Level 65
#488 Cresselia - In the strangers house near Yamaji Town, you have to complete a puzzle within the house to gain access to the Lunar Wing. Once you have that Cresselia will be waiting on Marvelous Bridge at Level 68
#638 Cobalion - It's first met on Route 6, after this it will appear in Route 13 to be captured. It's at Level 45
#639 Terrakion - It's waiting on a hidden platform on Route 22. It's at Level 45
#640 Virizion - It stands at the west of Route 11. Available for capture after the area has been frozen over.
#643 Reshiram [White 2 exclusive] - After you've defeated the Elite 4 N will appear in the ruins of his castle. He will battle you with Reshiram. After the Pokemon will convert back to the stone where it can be taken to Dragonspiral tower's summit and be caught. It's at Level 70
#644 Zekrom [Black 2 exclusive] - Same case as Reshiram. It's at Level 70
#646 Kyurem - It can only be capture at Giant Chasm. After capturing, Kyurem will leave behind the DNA link for changing it's forme. Black Kyurem for Black and White Kyurem for White. It's at Level 70
#646 Black/White Kyurem - Can only be obtained by using the DNA link on Kyurem in either Black or White.
Credit to [url="www.serebii.net]Serebii[/url] for the Mesprit image and Information. Will be updated as new info comes.
