Stalker

The Stalker is a rare/uncommon NPC that has always a higher level from 30-70 and can be found anywhere, from low level areas to high level areas. He is known to follow anyone, in the party you are in, who has recently killed any boss enemy. His presence is made known by taunting the player with messages in the same fashion as bosses. The screen also flickers for the player during these taunts. After three taunts, the stalker teleports into the mission which can be heard with a unique sound effect. He also uses similar abilities to other warframes and carries the Braton Vandal. This enemy has shields but its amount and regeneration speed is unconfirmed. It may be a rogue Tenno (unconfirmed). However, one of the notifications he gives the player mentions he is there for a revenge which suggests he may be an assassin. Stalker can be killed fairly easily due to a nerf in a recent update. After his HP drops below 10% he sits down and disappears in a cloud of black smoke.

The Stalker has been nerfed in a recent update.

Appearance
Seemingly Stalker has a chance of spawning anywhere where the player is. No boss needs to be slain, he just randomly spawns.

Abilities:
It uses already existing abilities from other warframes.


 * Ash's Shuriken


 * Ash's Invisibility


 * Ash's Teleport


 * Excalibur's Slash Dash


 * Rhino's Charge

Strategy
Stalker attacks with high damage output, he can kill an inexperienced player with a few melee attacks. The obvious strategy is to keep moving to avoid his gunfire. The Stalker is similar to Ash because of his speed. If he disappears without leaving a body after defeating him once, it means that he's not dead and may attack you again later in some other mission. He does not reappear in the same mission twice. The Stalker targets only one player at a time, but he is also easy to take out if your weapon puts out enough damage to take out his shields.He does not get distracted by Loki's Decoy or Saryn's Moult.

If the player that is targeted is playing as Loki or has the Shade sentinel with Ghost ability, then becomes invisible,  the Stalker will be unable to kill the player and will wander around until he disappears. (Confirmation needed!)

Trivia

 * The Stalker won't appear to warframes of level 5 or lower.
 * In a team, he will contact only one player, but all players will see the lights flickering before his appearance.
 * If he kills the player he came for, that player cannot be revived by other players. The stalker disappears afterwards.