Haunt

Haunt marks the opponent that defeated you with a position-tracking mark for 9 seconds (as of Version 2.7.0). This mark can be seen by the player with the ability and their team, similar to Point Sensor or Echolocator. This ability is restricted to clothing as a main ability.

As of Version 2.6.0, Haunt also has a Damage Up, Defense Up, and Run Speed Up effect when the player with Haunt is marked by Point Sensor, Echolocator, or Haunt.

In-Depth Ability
Haunt is good for players who usually play on the flanks or run support, or try and stop enemies from out-flanking their team. This is because if a flank or back is lost, then the team is notified that an enemy may be coming up from the behind.

Teammates should be able to avenge their fallen allies much more easily.

Because of its interaction with Point Sensor and Echolocator, Haunt can be considered a pseudo-counter ability for these sub and special weapons.

Use
Haunt activates automatically if the player gets splatted by another Inkling. The Inkling that splatted the player will be revealed to the splatted player's team, which allows them to avenge their death. Its location reveal has the same look as the Point Sensor and Echolocator. Its effect is reduced by Cold Blooded.

Gear
Haunt is the main ability of:

Mutual exclusivity
Since this ability is found as the main ability only on clothing, other abilities found only on clothing are mutually exclusive with it; in other words you cannot have them together. These abilities are: Cold Blooded, Recon, and Ninja Squid. In addition, since wearing the Splatfest Tee is mandatory during a Splatfest, these abilities cannot be used for the duration of those events.