Eximus

Leaders are special 'elite' variants of standard enemies introduced in Update 12 that can appear in any mission type. They come with special abilities, some of which are similar to Tenno and are sometimes much stronger than an average member of their faction, though effects vary from type to type. Leaders spawn 10-15 levels higher than the level average for the map, and can pose a reasonable challenge for underequipped or inexperienced Tenno.

Almost any base unit type (Osprey, Lancer, MOA, etc.) or boss can spawn as a Leader type; Leaders can easily be identified by their special auras, and frequently possess unique or customized textures/skins to make them more visually distinctive.

Scanning a leader unit counts as a scan of the base unit's type - they do not have unique codex entries.

Blast
"Defends itself with a radial Blast attack."

Blast Leaders are not noticeably more durable or dangerous than their base type.

Caustic
Heat based attacks and auras.

Energy Leech
A Tank that drains Energy from Nearby Enemies.

Guardian
"Restores shields of nearby allies."

Guardian Leaders are especially durable, gaining a significant boost to their own shield durability as well. They release radial shield-restoring pulses, similar to the healing wave effect of Ancient Healers.

Ice
"Cold based attacks and auras"

Cold Leaders can generate a temporary Snow Globe to protect themselves and allies. Unlike conventional Snow Globes, their version follows them when they move as opposed to being stationary, making it much more dangerous. They have additional ice-based attacks as well.

Ice Leaders are among the most dangerous variety, as closing to melee will subject you to ice damage and/or slowdown effects, whilst their snowglobe protects them from ranged attacks. Certain targeted powers, like Oberon's Smite, can damage the target through the snowglobe.

Lifesteal
Enemy with a life stealing attack.

Mag(netic)
Attacks are Magnetic.
 * This is the same effect as the Infested Disruptor's special attack, draining enemies of shields, power, and disrupting the screen.

Corpus Crewman variant seen with sub-text; "Electric based attacks and auras". Generated a constant magnetic aura that caused HUD disruption, shield loss, and energy loss.

Venomous
"Toxic attacks and auras"

Toxic attacks and aura.