A Seeker is a type of Challenges in exploration scenarios. Seekers are able to Move on their turns and, when applicable, can be seen from adjacent unblocked regions.
Seekers rarely deal damage, instead functioning by causing the players to lose Stealth Tokens. Seekers are used exclusively in stealth type scenarios.
Most Seekers follow a preordained patrol route and order of movement and Actions on their turns. This can be interrupted if a Seeker becomes Alerted, in which case the Seeker will actively seek out the PCs to the best of its ability (noting that it doesn't actually know where the PCs are located). Seekers become Alerted when they cause the PCs to lose a Stealth Token, find another Seeker that had been previously defeated and not hidden away, or through various other activities described on their cards.
Many Seekers have only 1EP and can be readily defeated by a PC through a stealthy surprise attack. However, this is quite risky as Seeker Reactions are typically dangerous with high Endure dice and powerful effects.
If a Seeker is defeated, a PC may hide the defeated Seeker with an Action. Doing so prevents other Seekers from becoming Alerted once they enter the region. Seekers only become Alerted in this manner when they enter a region; Seekers do not become instantly Alerted once a Seeker in their occupied region is defeated, for instance. If there is no place to hide a defeated Seeker within a region (as determined by the DM), a PC may use an Action and Move together to drag the defeated Seeker into another region. This does not hide the Seeker, however, which can still be discovered in the new region by another Seeker entering it.
Seekers start with a -1 in each Stat Track.
A Seeker that both respawns and pursues the PCs through the scenario is worth 1 PC of equal level. Otherwise, the Seeker is worth half a PC of equal level.
See also: Creature, Environ, Obstacle, Trap, Player's Guide Chapter 5: Exploration, DM's Guide Chapter 3: Running Scenarios