Stalker Mode

A unique gameplay variant, unofficially dubbed Stalker Mode, was first unveiled during TennoCon of 2017. The proof-of-concept allowed a player to taker over the role of the usually AI controlled (pre-Second Dream) Stalker instead.

While there had been originally no words on any plans to continue or properly implement the game mode for a long time, apart from the occasional use by developers or at events, it had since been officially stated that a variant of it is planned to be added to the game some time in the future, most likely through/with its own accompanying syndicate mechanics.

Gameplay and Deviations
Due to the unique nature of the Stalker a bunch of the usual gameplay mechanics and conventions were slightly altered or adjusted. Additionally a few of the features are/were unique to the fact that the implementation originally presented was functioning through a specific dev-build client and account and as such can and most likely will change on any possible proper implementation of it in the future.

Navigation and Inter-Mission

 * Instead of the Orbiter serving as the inter-mission hub, the Player Stalker would return to Hunhow's Lair (as shown in the Second Dream opening cutscene).
 * Instead of the Navigation console, the only interactable object available there was the War Hunhow fragment lodged in the ground with an "Eradicate the Dreamers" interaction tooltip.
 * The Stalker's Star Chart (humorously nicknamed "Stalk Chart") was tinted red instead of blue and (logically) restricted to the pre-Second Dream locations, so without Lua or the Kuva Fortress available.
 * Also not listed was the Orokin Derelict due to its special non-open-group-match-making property, though this was apparently rectified in a later iteration of the game mode, where it appeared as a valid location.
 * Additionally all location names were suffixed with the number of valid open Squads currently operating there so e.g. "Earth - 21".
 * The Player Stalker was unable to launch missions on their own, only to "join" squads already in progress.
 * The "Searching for open squads..." tooltip was appropriately replaced with "Acquiring targets...".
 * The failed match-making tooltip was likewise replaced with "Target has escaped!".
 * Apart from searching for targets based on Nodes, the Player Stalker also had the ability to directly "search" for specific targets with a unique "/stalk [NAME]" chat command which would either automatically force match-making or return "Target not in mission" on failure (otherwise chat access was entirely disabled).
 * Instead of the Landing Craft loading screen, the Stalker Codex entry diorama was used (though with the target player Tenno missing).

Mission and Gameplay

 * Upon successfully "spawning" into a mission in progress, the targeted squad would see and hear the usual "flicker lightshow" and taunt transmissions for the selected target player, during this period the Player Stalker was allowed to move around (at walking speed) invisible and impervious to any damage/effects but with locked weapons, to reposition themselves for their "reveal".
 * Ironically the transmission would also be visible to the Player Stalker just with a generic "Tenno" in place of the respective marked player's name.
 * Once the third flicker had occurred the Player Stalker would be locked in their invincible standing-up animation while turning visible.
 * The squad would appear to the Player Stalker just like in regular gameplay, so with their respective Frame icons on the minimap and their silhouettes and names visible through terrain.
 * Also the majority of the usual HUD elements were not displayed, such as health/shields/energy or weapons/ammunition instead replaced with a smokey screen vignette border, though the mission's objective and on-screen markers were visible.
 * The Player Stalker had not any access to the unique abilities of the Stalker, only the basic armaments of Dread, Hate and Despair as well as the Stalker's increased level-scaling durability/survivability (health/shields/armor).
 * The Player Stalker's "mission" would be successful (with the accompanying transmissions and kneel-disappear animations) once a squad member would be killed or ended prematurely once he was brought down to the 10% health threshold.
 * Alternatively the mission could be (traditionally) ended by killing the defense objective/rescue target/etc. depending on the mission type, as the Player Stalker was hostile to all factions.
 * Any encountered hacking console would auto-solve themselves on any input by the Player Stalker.