For the "Brotherhood" achievement, you need to unlock, then purchase the following 10 characters:
Blob
Emma Frost
Juggernaut
Magneto
Magneto Acolyte
Mastermind
Mystique
Pyro
Sabretooth
Toad
A few of these are found and unlocked throughout the story mode. The rest are found by traveling around Manhattan and completing the associated challenge to unlock them.
Toad has 3 separate challenges associated with him, composed of jumping around on lily pads (very easy). After beating his first challenge (located behind the X-Men mansion on the beach), the 2nd will be unlocked at the western coast of the city, in the Industrial District by the water. After which, the third and final challenge will appear on Liberty Island (where the Statue of Liberty is located), on it's wooden pier. Completing this challenge with then unlock Toad.
Blob is earned by completing the "Put Up Your Dukes" side-mission, indicated on the map as a red circle with a silver barbell weight in the center. You will need a total 75 Gold Bricks found to unlock this mission.
Here is a quick guide for "Put Up Your Dukes":
- Use Wolverine's Senses to find a way to climb the wall on the left, then climb up and destroy the vending machines. Build the remaining pieces into a giant water sprayer.
- Next, destroy the water coolers and build the remaining pieces into a water cup. Fill the cup with the water sprayer (aim near the top), then use telekinesis to lift it into the ring, where Blob will come and drink it.
- Destroy all of the cabinets in the upper left corner, including the fridge on the other side of the stairs. Using telekinesis, lift the mid-sized piece onto the biggest, then lift the smallest piece on top to create a food platter. Lift it into the ring for Blob to eat.
- Finally, head towards the right side and use telekinesis on the treadmill to speed it up until it explodes, leaving behind pieces for an oven, which will then pop out some food. Using telekinesis, lift the food into the ring for Blob to eat, and will complete the level.
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-Dan