Nightmare Mode

Nightmare Mode is a set of random challenges added in that increase a mission's difficulty. Mission nodes under the effects of Nightmare Mode have a scarlet highlight and a white swirl icon above the node's name. You can only see and select Nightmare Mode missions on a planet once you have completed all the missions on that planet. The game randomly selects missions for Nightmare Mode from any planet every 8 hours. You can access Nightmare Mode Trials by building a Nightmare Mode Trial key.

As a reward for accepting the challenge, completing the mission will result in a special prize of a Rare Nightmare mod with dual effects.

Mechanics
To unlock Nightmare mode, one must complete all of the missions on the planet. You cannot start a Nightmare mode mission if your Mastery Rank is 0.

From  onwards you may choose whether to run the mission in Nightmare Mode or not. If some of the players in given cell do not have Nightmare Mode unlocked, only those with it unlocked should select Nightmare Mode or else the mission will start normally.

The rewards for this mode are randomized, but once a player completes a mission the nightmare node on the respective planet disappears until the next rotation.

Beginning in, eligible Alert missions have a 5% chance to become Nightmare Alert missions. Upon successful completion of the alert, players are awarded a specified Nightmare mod. However, the No Shields modifier is always one of the selected modifiers (unless the mission type is a hijack, shields are needed in order to make the convoy move).

Challenges
All Nightmare Mode enemies are significantly increased in level and will have 3 times the damage output, and in some cases are replaced with more dangerous versions. For example, instead of spawning Grineer Lancers, the map may spawn more Elite Lancers in their place. In Nightmare mode, lockers won't drop ammo but enemies still will. Environmental Hazards can also appear as usual.

Up to two of the following challenges may occur per mission, and each modifier has an equal chance of being selected:

Mission Rewards
Possible rewards on completion include:


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Trivia

 * At the time of Nightmare Mode's introduction there was a No Minimap modifier that also removed the objective indicator. This was removed in  following player complaints.
 * added the No Shields modifier to the Energy Drain modifier, as well as reducing the chance of getting the combined modifier.  simply split the modifiers altogether.
 * added the mod rewards from the Arid Fear Event (Shred, Vigor and Lethal Torrent) in Nightmare Mode's reward pool.
 * There seems to be an increased drop chance of resources, mods and other pickups. Users report finding many more mods than usual on missions.

Bugs

 * Host Migration will sometimes revert the mission to a normal state, removing all modifiers and resetting enemy levels to the mission's original range. Nightmare mods will still be rewarded however.
 * The Health Vampire and Timer modifiers will take effect as soon as the mission begins, i.e. as soon as the beginning cutscene starts.