The following walkthrough was co-written by Eldin and Stella to help other gamers who might be having trouble beating the Legend time trials.
Time Limit: 04:15
It may seem counterintuitive, since it's a hard level, but we actually recommend doing this Time Trial first. The strategy is almost the same as for the regular level, and once you beat the Time Trial, you'll have unlocked the one-shot kill cheat, which is super helpful in the others. Also, if you've just beaten the game, this level will be fresh in your mind. If you can't manage it, try and complete England to unlock the Bulletproof Lara cheat. Then go for Bolivia Redux next.
You don't have much time for this level, but you don't really need much if you stay focused and don't panic. When the level starts, immediately switch to Excalibur...
...and start taking out the mercenaries. Keep moving, avoid their grenades, and don't fall off the edge, just like in the regular level.
When there are only one or two enemies left, top off Lara's health and pick up as many health packs as you can carry. Then if you die while fighting the creature, the game will reload with full health and more in your inventory.
Finish off the last mercenary and skip the cutscene.
This is entirely optional. Do what works best for you, but if you're having trouble keeping the monster targeted, you may want to pause and set the Combat Mode to Advanced Toggle. This can make the camera angle go crazy at times, but it will ensure Lara targets the creature with every slash of her sword.
Now get in there and beat that thing! Don't hide. Don't hesitate. Just start blasting away.
Run and jump toward the creature, getting as close to it as you can. Jumping forward with a weapon drawn also makes Lara do a forward flip, which makes it a little harder for the creature to blast her.
Move in as close as you can—stand right under the monster if possible—and keep slashing away with Excalibur.
With this technique, it won't take long before it falls down for the first time. Lara will already be standing right next to it, so adjust her position if necessary and press Interact to stab Amanda with the sword.
Now the whole thing starts again. If the creature flies away, follow it.
Again, keep swinging the sword and move in as close as you can.
Lara will definitely take some hits. This is why you made sure to pick up all those health packs during the fight with the mercenaries.
Again, slash away at close range, and when the creature falls again, move in and press Interact to stab Amanda.
Repeat the sequence twice more: Stay close, right under the monster if possible, and slash, slash, slash!
The last time, it won't take long at all since the creature's health is already so low.
Press Interact one more time...
...and that's the end for the Unknown Entity.
Bolivia Redux complete!