Use Frodo to enter the hatch as well, then go to Sam's area. Switch to Sam, enter the hatch, go down the lava floor below. Switch to Frodo, light up the cave, walk to the right, then smash the rock. Smash the objects near the slider, build a pillar, push the pillar to the left side, make Frodo stand at the right platform, use Sam to jump up the ledge above Frodo's platform on the right, use the rope to make it across the left platform, wait until Frodo moves to the top of the pillar, then push the pillar to the right. Use Sam's rope to pull down a huge rock, then walk up. The name implies that you were trying to force the ring into the fires of Mount Doom before it ended up with Bilbo and Frodo, thereby undoing the whole plot of LotR. Use Sam to jump across, dig up and build a bridge for Frodo, then walk across. Yes, the achievement is for jumping into the lava with Isildur in the last stage of the Prologue level, inside Mount Doom.

Use Frodo to walk at the plank on the left, then fall down to the left platform to make Sam go up. Make Frodo stand on the platform at the right, use Sam to jump up the middle rock and then to the left platform to elevate Frodo. Smash the objects blocking the cave, cross the cave using Frodo, use Sam to pull down the rocks above, cross the rocks again. Avoid the burning flames, then use Sam to climb up the bars, walk across the lava rocks as Frodo.

Use Frodo's phial to light up the dark cave, push the rock inside, use Sam to dig a rock, throw the rock at the target above, cross the rocks to the next area. Switch to Sam, jump up the bars, pull yourself up to the very top, use the rope to climb up the ledge, stand atop the platform on the ledge to make Frodo's platform go up, walk across using Frodo.

Have Frodo stand atop the first platform that you'll see after you walked across the lava rocks. Frodo can't jump here, so use Sam to jump across the island in the lava, then use the rope to pull down rocks so Frodo can walk across. Walk up, break the two brown boxes below the ledge, build a ramp, then walk up ahead.

Mount doom lego lord of the rings