Brolders are basically living boulders that hide underground, then come out of the ground whenever you get close enough. Once above the ground, the Brolder will really do nothing but roll towards you, where touching it on its sides will cause damage. If you happen to jump on top of the Brolder, though, it will revert to a normal-looking boulder, allowing you to pick it up. Tossing it on ground does nothing, but considering Brolders inhabit lava-filled levels, throwing it in the hot liquid will defeat it. However, most Brolders will continually respawn indefinitely. Note that it will come alive again once enough time passed, whether you’re carrying it or not.