The following is a guide intended to help players make their way through the puzzle in Stage 5's Underground Lake from Riviera: The Promised Land. This is a subarea of Mireno Cemetery located deep underground; unlike the Seasonal Forest, however, this is a mandatory route and can prove to be confusing to some. The key to advance is using the Ankhs to manipulate the water level; the idea is to place the correct Ankh in their altars.
The player has to figure out which ankh belongs in which altar. If you wish to just get through the Lake, the list of correct Ankhs is as follows:
Some optional events will be skipped if one simply puts the correct ankhs in their proper altars. Let's start from the beginning. First, like before, place the L Ankh in the Red Altar and proceed. You should now be able to access that chest in the second room, which is a roulette chest. From here, move down, then right, and enter the next altar.
In the Yellow Altar, first place the A Ankh and head back. Backtrack one room and collect the Mana Wisp for some stat boosts. Return once again to the Yellow Altar and remove the A Ankh; replace it with the T Ankh, and leave. You can now head left, and up twice to a previously inaccessible area which will have a chest containing a Wyvernzem x50. After that's done, go back to the Yellow Altar yet again and replace the T with the I Ankh.
After returning to the lake, head upwards twice and go into the Blue Altar; offer the T Ankh here and return. With the ankh in place, the Dragon Buster x15 should be unveiled; remove it via a minigame to obtain. Move down once, and you'll find a black boulder. Have a spare Trigger Point available and inspect this twice in Look Mode. If you succeed in moving it out of the way, it opens the path to an important secret path with an optional boss, the Gate to Hell. Completing this area will earn you the Key to Hell, which unlocks the bonus chapter.
After that's over with, backtrack to the Yellow Altar and replace the I Ankh with the X Ankh. Move upward twice, then right. The green portal is actually a trap and you'll be attacked by an Elemental trio. Head back to the Blue Crystal Altar and replace the T Ankh with the A Ankh. If you wish to partake in the infamous skipping stone minigame, you'll now have access to it; it should be in the room east of the Blue Altar's entrance. At this point, you may proceed to Pieta or head right once then down two times to the chest that requires the Thief Manual to open, containing a Tarot x5.
If you came here from the Mireno Cemetery Stage Guide, click here to return.