History
Players must help protagonist Zoe Castillo navigate the technological, Sci Fi world of Stark to solve a mystery involving the disappearance of her ex-boyfriend. Along the way, Zoe's investigation leads her to April Ryan, another of the game's three playable characters, who picks up the story in the magical world of Arcadia. April is the character who faces the challenge of having to open the altar door.
Location
In Chapter 5, April takes center stage, exploring the same subterranean city Zoe visited earlier in the game. Continue along the city's main path until you see a troll open a door into a chamber. Wait for the troll to enter and then run through the door before it closes. When inside, look for another door positioned in the far left of the room, next to an altar. This door requires a combination, meaning you'll need to use stealth and strategy to open it.
Hide
This altar chamber features several pillars. Stay in the shadows along the pillars and then duck down behind the altar to hide. Wait there until another troll approaches. But stay hidden. If you attempt to engage the troll or if the troll spots you, it summons an invincible beast that means certain doom.
Focus
While continuing to hide, activate the Focus Field function to zero in on the locked door as the troll enters the secret code. After the troll enters and the door closes, leave the safety of your altar hiding place and re-enter the secret code to unlock the door. Go inside and take the staircase that leads down to find the next key item in your quest.
Considerations
Many gamers experience difficulty opening the altar door due to failing to use the Focus Field function or to activating it too soon. If you do it properly, you should view a cut scene showing the troll's every movement. If you don't get the cut scene, you know you didn't time things correctly. Simply remain hidden behind the altar and wait for another troll to come along and open the door.