Parallel Worlds

Parallel worlds (also known as West/East worlds) are worlds which can be accessed by digging through the giant rock walls at the edges of the world. They have a nearly identical world layout as the starting world, but are missing certain key structures such as the Lava Lake and the Giant Tree. They also have new wands, max health upgrade pickups, and perks. Any biome visited in a parallel world will be affected by the same biome modifiers as the equivalent level in the original world, and will have 'East' or 'West' prepended to their name accordingly (e.g. 'West Holy Mountain', 'East Desert'). Amusingly, this is true even of biomes with 'The' in their name, such as 'West The Vault'. Only one prefix will be added, regardless of how many worlds over the player is.

Navigation
Entering most portals while in a Parallel World will send you back to the starting world, so it is generally required to dig into the Holy Mountain in order to progress to the next area. This quirk however means that it is very easy to return to the starting world.

However, activating a Meditation Cube portal or Buried Eye portal in a Parallel World will create a helpful shortcut to/from the Main world, because the exit-portal from those rooms will always lead to the most recently used entrance-portal.

Reaching a Parallel World
To reach a parallel world, you will need a good digging wand with powerful spells like Black Hole, Ground To Sand or Matosade. Not only will you need to dig through a giant wall made of Extremely Dense Rock (which is roughly the width of the Lake), but unlike most, it has a part made entirely of a deadly material known as Cursed Rock. Crossing the section in its core will cause heavy damage to you while within the area.

Digging through the wall
To dig through the wall, the fastest method is to bring a wand with Speed Up or Light Shot, and at least 6 black holes (possibly doable with at least 4). If you don't have any speed modifiers then you may need more than 10 or 12 black holes to pierce the whole wall (a wand with Black Hole as an Always Cast is a godsend for this). The Projectile Repulsion Shield perk can significantly increase the velocity of Black Hole, but can introduce some terrible inaccuracy. This issue can be fixed with Horizontal Path.

Alternatively or in addition, a high–mana charge speed wand with Quadruple Scatter Spell Luminous Drill and Chainsaws can allow for a player to make slow but steady digging process through the wall. One can end up on the other side of the wall using a wand with ~150 mana charge speed with this method in under 20 minutes if they are skilled at digging. The benefit of this method is that it doesn't require any limited-use spells.

If you happen to obtain the spell Matosade (most likely from killing the Sauvojen Tuntija miniboss) and also either get the Unlimited Spells perk or one of the Greek letter spells (potentially from the Ylialkemisti miniboss), you will be able to very easily and quickly dig through the entire cursed section with just 4-5 Matosades.

Matter Eater sadly does not dig through Cursed Rock.

Surviving the damage
It's important to note that even if you remove all the Cursed Rock, you will still be damaged from being in a cursed area. However, the damage from being in the area is much lower than the damage you take from touching the actual Cursed Rock, so it is advised to stay airborne as much as possible when crossing through the worlds. Having the Slime Blood perk will make it easier to stay airborne, but might also make it harder to stain yourself with Ambrosia.

There are a few approaches to tackle the damage issue. You can:
 * Simply have a large HP pool. With over two thousand HP, you will be able to casually walk on top of the Cursed Rock.
 * Constantly heal yourself with some sprayed bottled Lively Concoction.
 * Block the damage entirely with Ambrosia. Combine with teleport for best results, as normal movement dissolves it quickly.
 * Polymorph into a Jättimato, Helvetinmato, or a Kalmamato using Chaotic Polymorphine and tunnel through the dangerous section in one go. It might take a few tries to get the correct form and being as safely close to the Cursed Rock as possible is recommended. The normal Mato and the Pikkumato don't have the speed or the health to cross the gap without dying. But keep in mind that going over 80 polymorphs has a chance to permanently trap you in the polymorphed form.
 * Dig through the whole section first, then use Teleport Spell to quickly hop through it. This might require around 200 hp, as long as you don't touch the Cursed Rock.

Each method has its merits.

Differences to the Starting World
Many generated structures cannot be found in parallel worlds. Where structures are missing, they will be replaced with a completely empty block, and the terrain around it may therefore look unusual or not connect properly. This is most clearly seen where the Lava Lake would be, at the connection to the adjacent shaft.

Areas where visibility is impaired with default Biome Modifiers such as the Dark Cave, retain this trait in the space where they would have rendered.

List of missing things

 * The boss and 3 minibosses:
 * Kolmisilmä
 * Kolmisilmän koipi, the miniboss at the top of the Pyramid, despite the pyramid still existing.
 * Limatoukka, along with the buried skull deep below the Power Plant.
 * Syväolento, in the Lake
 * All the others can still be fought and drop their usual rewards, including additional special items.
 * Many specific locations:
 * The Giant Tree, including the Kantele and pillars.
 * The Dark Cave, including the health pickups, but the darkness will still be there.
 * The Lava Lake, including the orb below it. Making the amount of orbs in the world 10, instead of 11.
 * In New Game Plus worlds, this orb is still present in both main and parallel worlds, instead buried deep into the Extremely Dense Rock somewhere off the right side of the holy mountain layers, though the exact placement is random.
 * The Hiisi Base's: Shop, Hourglass, and Anvil.
 * The entire Laboratory, including its Holy Mountain and the boss.
 * Therefor parallel worlds only give you 6 perks, 6 health/spell restores, and 6 shops, instead of 7.
 * The Lake Island, making the Essence of Fire unobtainable in parallel worlds and also making it impossible to create the portal to east.
 * The giant skull in the Desert, making it impossible to create the portal to west.
 * The fish pond to the east of the mountain entrance.
 * The Moon.
 * The Gourd cave in the western wall by the Cloudscape.

Besides those things, everything will be there. Even the secret rooms and The Tower, though, of course they require digging to reach, as portals would bring you back to the normal world. The Huilu and its notes are also available.

Orbs of Corrupted Knowledge
The Orbs of True Knowledge in parallel worlds are red instead of the usual color, and are instead known as the Orbs of Corrupted Knowledge. These orbs function as normal except that the health upgrades they come with cause the player to take damage over time equal to 44% percent of their max health, when picked up. This damage generally won't kill the player, unless they are in New Game Plus. As usual, you can block this damage with ambrosia. In addition, it is possible to pick up the Orb without taking the cursed health upgrade by standing on its very side, when picking up the orb. Unlike normal orbs, the corrupt orbs never contain any spells and always just contain a cursed max health upgrade.

Collected corrupted orbs add to the orb counter in the top right, further increasing the health of the final boss in the starting world (if still alive). Each specific corrupted orb can only be collected once per east and west world. For example, after collecting the pyramid orb in the first east world, it won't be possible to pick up another pyramid orb in the next east world, but it will still be possible to collect the orb once more in the west worlds. With 11 orbs per world, this means that the maximum amount of orbs that can be collected in a run is 33.

Currently, the lava lake orb does not spawn in non-New Game Plus parallel worlds, making 31 the max amount of orbs that can be collected without going NG+. 33 orbs are required for a secret ending and reward.

Shadow bosses
From the Epilogue Update onwards, there's a chance that a Shadow copy of either the Ylialkemisti or the Sauvojen Tuntija spawns anywhere in the Surface of PWs, named Alkemistin Varjo and Sauvojen Varjo. They are characterized by a dark purple tint, vanishing into smoke when defeated and leaving no corpse or rewards. They have their own counters in the progress menu however.

Issues and Crashes
Visiting too many PWs in one game may cause the game to struggle due to the sheer size of the save. Eventually, the game may crash due to memory overload. Therefore, a less resource-intensive, safer alternative to going to parallel worlds is to start a new game, and port the old 'player.salakieli' file to the new game to retain your perks, health and items, though some players may consider this cheating. Remember that the player's position will be the same in the new world as the old game, so you may get stuck in a wall if this is done while you are underneath the surface—and you will be in a parallel world in the new game if you ported it from an old one while the player was in a PW.

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