Our Xenoblade Chronicles guide features a comprehensive walkthrough and additional info on the endless amount of optional content in the game.
Walkthrough: Entia Tomb
When you have control of Melia again, take note of the mini-tutorial. Since you’ll be fighthing alone, the information it provides in invaluable. The trick is to use an elemental art, then use her elemental discharge to use that elemental against the enemy, dealing greater damage than a stand alone attack. Though Melia’s talent gauge will appear greyed out, it’s definitely active.
After a few brief trial battles, you’ll regain control of the rest of the team. Be wary when exploring the tombs. Enemies generally aren’t visible until they are right on top of you, so if you try to run from a battle, it’s likely that you’ll just attract more enemies. It’s best to stand your ground and handle each encounter individually. As you follow the goal arrow, you’ll have the choice of heading through a long hall to the north, or a ring shaped room towards the east. Head east when you are done exploring. The circular room features a spiral-ramp that will take you to the lower level. Once there, the goal marker is in plain sight. You’ll come to a room with a huge orb in the middle. To get to the platform in the middle of the room, use the walls nearby to climb over to the bridge.
When you get there, you’ll face a lvl 36 hulk of a monster, Rufus Orluga. Keep a healer handy, and be wary of his ability to inflict your team with the Arts Seal debuff. Avoid using a Chain attack in the case you need to revive fallen team mates. This battle isn’t terribly difficult so long as you are on an even level, but it’s not uncommon for one of these guys to incapacitate a team mate.
As you head east towards the next goal, examine the chambers along the northern wall of the long hallway. There is a hidden passage that leads to an area known as the Secondary Treasury. You can obtain a valuable piece of headgear, but be warned, there’s a level 38 enemy guarding the treasure.
Continue forging eastward. You‘ll reach the tower of trials bridge at the end of the hallway. Climb the wall on your left to reach the platform above your current position. There’s another Orluga Rufus waiting for you, level 37 this time, and he’s got a companion as well. You know the drill. Take ‘em out.
Climb up the southeast wall once the path is clear. There’s a final Orluga waiting for you on the next level. Once he’s gone, head up the ramp along the north wall. You're approaching a boss fight, so assess your arts, equipment, and, team.
The strategy for this fight is quite simple. The Telethia needs to have his aura broken using Shulk’s Purge Monado Art. Between purges, use Shulk as your secondary healer, and allow him to auto-attack so he can refill his Monado Talent Art gauge. Thankfully, if you neglect to ready the Monado’s powers in time, you can attack the female Entia. Switch your target to her so you can auto attack. While you won’t do much damage against her with the Monado, this will afford you the opportunity to recharge it’s abilities.
This is the one downside to the fight. You need Shulk to break the Telethia’s aura, but he won’t be able to do any damage during the second half of the battle with the Monado. If you are level 40 (or higher) you may not need Sharla’s healing skills during the fight (resorting to Shulk’s light heal) which means you can double up on the heavy hitters, namely Reyn and Dunban.
There is an apparent mistake in Special Lever 2 for Regbuilding Colony 6. It says defeat Earth Nebula at Sap Cave. I was never able to find a Sap Cave, but I was able to defeat Caris Nebula at the brog lake just before you get to Nopon Arch.