Nullifier Crewman

The Nullifier Crewman is a Sniper Crewman that carries an energy field generator on his back. The spherical field not only prevents projectiles from entering (similar to Snow Globe), but it also dispels any present buffs as soon as players enter it, as well as preventing any abilites from being cast within its radius, as well as destroying most powers in it's radius. Firing at the globe causes it to gradually shrink and eventually dissipate the globe altogether, although it will regenerate after a brief period.

Tactics

 * Nullifier shields use the following mechanic to determine damage dealt to it:
 * Nullifier shields have a minimum and maximum damage per shot dealt to it - 100 damage at minimum, and 400 damage maximum. Any hit that deals less than 100 damage will be buffed to that amount, while any shot that deals more than 400 damage will be nerfed to that amount. The buffed/nerfed damage values are not displayed by the damage indicator, it will still show the unbuffed/unnerfed values!
 * The damage dealt is then altered by the Nullifier shield's shrink rate per shot, which is 6% of its current size.
 * The formula for determining damage to the Nullifier shield is Damage/100 * Base Shrink Rate.
 * Example A: A Braton hits the shield for 18 damage. Since the shield can only receive a minimum of 100 damage, the shield takes 100 damage from that hit. The damage (100) is then divided by 100, which equals 1.0. This value is then multiplied by the shrink rate of 6% (0.06), giving a value of 0.06, which results in the shield being reduced by 6% of its current size.
 * Example B: An Opticor hits the shield for 500 damage. Since the shield can only receive a maximum of 400 damage, the shield only takes 400 damage from the shot. The calculation is thus 400/100 = 4.0 * 0.06 = 0.24, hence the shield will shrink by 24% of its current size.
 * The rate of shrinkage is based off the current size of the shield.
 * Hits are calculated per frame (framerate), and not for each individual pellet within a shot, i.e. a shotgun that shoots 6 pellets dealing 100 damage each for a total of 600 damage is considered as dealing 600 damage, and thus will have its damage nerfed to 400, resulting in a 24% reduction in shields.
 * Due to the Nullifier field having Object health property which nullifies Critical Hit damage, weapons that heavily depend on crits such as Soma, Synapse or Amprex can be less effective against it if the non-critical dps value is too low.
 * Being a sniper unit, Nullifiers are far less accurate up close, but get more accurate at medium and long ranges.
 * Splash damage from explosive weapons and powers originating outside the field are nullified, dealing no damage to anything inside.
 * The energy sphere will remove any buffs active on Warframes caught inside it, and will render the Nullifier immune to direct targeting by all Warframe powers, including AoE and indirect powers.
 * Despite being a Sniper Crewman, the Nullifier Crewmen's behavior is a bit different; they will not attempt to bash enemies who get too close, and much like Arctic Eximus they will not attempt to take cover or run away. Nearby allies will also head inside the Nullifier Crewman's sphere, making it harder to kill them.
 * Nullifier fields absorb hitscan projectiles and deflect physical projectiles. Care should be taken when firing heavy weapons such as the Penta  and Ogris directly at a Nullifier, as the grenades and missiles may be reflected straight back to their source.
 * Certain ability projectiles (e.g. the Shuriken projectiles) can home in on the Nullifier, but if the shield is present then they will bounce off of it like normal projectiles.
 * Due to the field having object health, weapons with very large clips, base damage and good ammo efficiency are most effective at dealing with Nullifiers.
 * The Quanta and its Vandal variant have proven to be very effective against Nullifier bubbles, especially when buffed by a Volt's electric shield as the beam passing through that shield gets a large boost to its effective range.

Tips

 * The Nullifier's energy field can be destroyed by melee attacks if they connect on the edge of its radius, which abilities like Valkyr's Hysteria could exploit, especially if paired with the Reach mod.
 * The minimum amount of shots required to make a regular Nullfield disappear is 6 shots and the minimum amount of time to do so is ~2 seconds. Since the maximum damage a shot can deal to a Nullfield is 400 it can be assumed that a regular Nullfield itself has 6*400=2400 health. Now if it takes at least ~2 seconds to make it disappear that means dealing more than 2400/2=1200 damage per second will not be of any use against a regular Nullfield. Because a Nullfield cannot receive more than 400 damage per shot and not less than 100 damage per shot, a minimum fire rate of 1200/400=3 shots per second is required to make a regular Nullfield disappear in 2 seconds if the damage per shot is 400 or a minimum fire rate of 1200/100=12 shots per second if the damage per shot is 100. Note that certain beam weapons like Ignis, Amprex or Quanta Vandal seem to have different properties when it comes to fire rate and damage per shot, for example Quanta Vandal is dealing more shots per second with less damage per shot than displayed in the user interface, even though the ammo consumption matches the u.i. (it is unknown whether this is a bug or intended).
 * Nullifier Bubbles are deactivated when they aren’t alerted.

Trivia

 * Nullifier Crewmen seem to have the same drop table as Sniper Crewmen.
 * Additionally, Nullifier Crewmen seem to wear the same suit that The Sergeant wears, albeit with yellow chest straps rather than white ones.
 * Oddly, the Codex image of Nullifier Crewmen seems to represent a standard Crewman with a black uniform and a jetpack used by the three Ranger variants in Archwing missions, whilst the in-game model has an additional helmet extension and a unique "core" pack on its back.
 * When summoned from Nekros, their shields will be the caster's energy color
 * A variant of the Nullifier Crewman can appear as a Capture target.

Bugs

 * As of, occasionally, entering the field may jam your abilities permanently if the Nullifier Crewman is killed before you can step out of the field. You can fix this by entering another Nullifier's field and exiting it before it dies.
 * The Codex Scanner can scan his sphere (provided it is up) for a successful scan. [Might be intended]