From Space Elemental Alien Variants for Specialists

As the Specialists make progress against the foes From Space, the otherwise-pink alien forces will gradually incorporate special variants of standard troops which take on an aspect of fire, lightning, or poison, collectively referred to here as elemental variants. Here is the low-down on what all variants have in common:

• Certain types of standard (pink) aliens (initially Crawlers and Hoppers) can randomly spawn as an elemental variant instead once a certain progress-related prerequisite has been met, with the frequency and eligible types increasing as further progress is made. Eventually, all types, including Smashers, will become capable of spawning as elemental variants.
• Damage-over-time effects (burning, shock, poison, etc.) have greatly reduced duration on all elemental variants, allowing them to ignore fire-and-forget methods of control, such as Electro Gun sweeps, which would immobilize or scatter their standard counterparts. Specialists are advised to stop these foes in their tracks using continuous methods instead, such as contact with Barbed Wire.
• All elemental Goopers and Boomers can create dangerous ground hazards by attacking and on detonation, respectively, which last for a long time before disappearing on their own. Specialists should take care to avoid these hazards as much as possible, even after combat has stopped.

Toxic aliens can be identified in the field by their green spots and unusually small stature for their type.

• Toxic aliens will poison Specialists if their attacks connect, causing their damage to apply over a 5-second interval. If the hit was taken directly to one’s health, the Specialist will be stopped from self-healing for the duration.
• Toxic Goopers and Boomers can create poison cloud hazards with the same appearance as those created by Toxic Flasks or the Toxic Goop Gun. Specialists should take care whenever both kinds of poison are present.
• Toxic aliens move faster than their standard brethren. Resourceful Specialists can use this fact to draw out toxic Crawlers from a crowd and dispatch them first.
• Toxic aliens are highly resistant to energy and crystal weapons, taking approximately 3x the ammunition to kill (relative to their standard brethren) when the following guns are used against them:
  • Toxic Goop Gun
  • Electro Gun
  • Specialist Electrogun
  • Plasma Gun
  • Crystalizer
  • Laser Rifle
  • Zapper
  • Particle Gun
  • Specialist Protocannon
  • Raygun
• Toxic aliens are vulnerable to all other weapons, going down more quickly than their standard brethren.

Fiery aliens can be identified in the field by their misshapen red maw.

• Fiery aliens will ignite Specialists if their attacks connect, causing their damage to apply over a 4-second interval. If the hit was taken directly to one’s health, the Specialist will be stopped from self-healing for the duration.
• Fiery Goopers and Boomers can create sticky flame hazards with the same appearance as those created by Petrol Bombs or the non-specialist Flamethrower. Specialists should take care whenever both kinds of sticky flames are present.
• Fiery aliens move slower than their standard brethren. Resourceful Specialists can use this fact to draw out fiery Crawlers from a crowd and dispatch them all at once.
• Fiery aliens are vulnerable to energy and crystal weapons, going down more quickly than their standard brethren when taking damage from the following guns:
  • Toxic Goop Gun
  • Electro Gun
  • Specialist Electrogun
  • Plasma Gun
  • Crystalizer
  • Laser Rifle
  • Zapper
  • Particle Gun
  • Specialist Protocannon
  • Raygun
• Fiery aliens are highly resistant to all other weapons, taking about 3x the ammunition to kill compared to their standard counterparts. For this reason, Specialists going solo are advised to keep a Plasma ammo-using weapon (other than the Black Hole Gun) in their arsenal once elemental variants of any kind start appearing.

Electric aliens can be identified in the field by their white streaks and unusually large stature for their type.

• Electric aliens will shock Specialists if their attacks connect, preventing them from taking any actions for 1 second as well as causing their damage to apply over a 5-second interval. If the hit was taken directly to one’s health, the Specialist will be stopped from self-healing for the duration.
• Electric Goopers and Boomers can create electric vortex hazards with the same stunning power as the aliens themselves. Specialists should take care to avoid these hazards while they’re being chased.
• Electric aliens move faster than their standard brethren. Resourceful Specialists can use this fact to draw out electric Crawlers from a crowd and dispatch them first.
• Electric aliens are approximately 50% tougher than their standard brethren and have no known weaknesses or resistances.