Enemy reveal radii is 1 for all enemy units, except a Chosen with the All Seeing strength (the reveal range is equal to the line of sight of a Chosen [explanation needed]) and Security Towers [explanation needed] (which were not disabled by a successful hack; destroying an active Security Tower will keep its detection radii, despite there is no tower any more -- obviously a bug).
Reveal chance in Shadow Concealment starts at 0%. The first shot will increase it to 50%, then 80% and finally 100%. As the reveal chance increases, so does the detection radii of the enemies, including a concealed Faceless mimicking a hostile civilian with detection radii of 1-2: the reveal radius becomes 4 after rolling the reveal chance at 50%, and is more after rolling the reveal chance at 80%. (a concealed Faceless will actually have the detection radii of 4+ if the reveal chance is 50%+, despite the GUI showing a regular hostile civilian detection radii of 1-2 on the mission map)
Because changes to Reaper concealment chance take place after a shot is fired, Silent Killer causes the chance of a kill shot being revealed to become 0% if it's the first shot. Thus with Silent Killer, a Reaper can participate in the fight by performing reliable kill shots from close range without ever breaking concealment. [explanation needed]
Reveal chance will be reset if a Reaper is revealed then re-enters Shadow Concealment. This can be done by using Shadow skill or Distraction talent.
A Reaper cannot re-enter concealment on the same turn the concealment was broken: breaking the concealment on the player turn will prevent re-entering the concealment on this same turn; however, if the concealment is broken during the enemy turn, the concealment can be re-entered on the following player turn. Note that it is possible to enter concealment with an adjacent enemy nearby, but that will imminently break the concealment, thus wasting the Shadow skill charge. [explanation needed]
Interacting with the mission objective targets - planting X-4 charges, subduing or picking up a hostile VIP, picking up a captured XCOM soldier, marking the supply crates, etc - will break the concealment with 100% chance. However, opening a loot box (on a mission with ADVENT Loot SITREP) will increase the reveal chance only by 10%. (the following Vektor Rifle shot will roll the reveal chance at 60%)
Reaper's Mobility is increased while staying concealed [explanation needed].
Claymore:
Claymore explosions deal 5 damage and shreds 2 armor in a radius of 3 [explanation needed], deployed at a range of 10 [explanation needed].
Shrapnel increases Claymore's parameters: damage is 8, armor shredding is 3, blast radius is 5 [explanation needed].
Claymore only costs a single action, and a Reaper firing at a Claymore does not break concealment.
Claymores are able to be detonated by any type of damage, not just firing. Consider using a grenade to start an ambush above a Claymore that's already placed to deal extra damage before the enemies perform their scrambling move.
Skirmishers' Resistance Order Weak Points increases armor shredding by 1.
Consider saving Claymores until after the Reaper is revealed in order to make the most out of Distraction ability (a kill with a Claymore puts the Reaper into Shadow concealment).
Remote Start is incredibly destructive and, when using on large objects like a bus, in a very wide radius. Take great care not to blow up civilians in retaliation missions.
Remote Start is able to far outpower any type of Grenade in other situations. Look for opportunities to use it against multiple hostiles; it is very likely to kill them.
Target Definition is very useful in setting up ambushes that do not trigger multiple pods.
Blood Trail increases Vektor Rifles damage by +1 against units previously damaged on the same turn. [explanation needed]
Also works with Overwatch shots against enemy during the enemy turn and on the following player turn.
Needle complements nicely with Silent Killer where shooting to kill is important. Combined with Blood Trail and it can deal up to 3 additional damage against armored targets.
Sting is useful when the reveal chance is at 80% above and retaining concealment is still important.
Considering the Reaper's critical chance is 0 by default, Soul Harvest can increase overall critical chance with every enemy they kill. This pairs very well with Silent Killer, and can build up critical chance up to 20% against any and all enemies they shoot, and boosting the critical hit rate of flanking shots to 60%.
Homing Mine does not replace Claymore, but both share the same charges.
Units marked with a Homing Mine are guaranteed to be hit when taking a Standard Shot at them, despite percentage to hit telling otherwise. This makes Homing Mine much more destructive than the standard Claymore, so consider using Homing Mine instead of Claymore when ambushing enemies.
Keep in mind that using the Reaper to fire on an enemy will still increase reveal chances regardless if they are hit with a Homing Mine (unless Silent Killer activates). Use other soldiers to fire on the target if you want to keep your Reaper concealed.
Banish:
Banish has penalty to Aim for each shot, -15%.
Banish sets the Crit Chance strictly to 0%, despite other ability bonuses and modifiers. (i.e. it is impossible to get a critical hit with Banish shots)
Banish is very useful for unloading on a high priority target, such as a Chosen or Alien Ruler. Having an Extended Magazine extends the power of this skill, allowing for more shots to be fired.
Banish reveals the Reaper before any shot is fired, thus the shots do not benefit from concealment-reliant effects such as Needle.
Remember that Banish shots roll to hit with every shot. Make sure you have a high chance to hit your target to make sure enough shots hit to kill the target.
Because Banish shots count as separate shots, Blood Trail affects every shot taken if applicable, and other on-hit effects like Shredder and Repeater instant kills also have a separate effect with every shot. Use this to your advantage and equip your Reaper to deal maximum damage.
Annihilate ensures that players get the most out of Banish. This allows Banish to become an all-around useful skill against both heavily armored, high priority targets along with groups of enemies.
Reapers cannot carry any equipment by default, so Tactical Rigging can allow a single item to be brought on a mission with them. Tracer Rounds and some armors work well with them, but there is little advantage to bringing Grenades since the Reaper already has Claymores. Bluescreen rounds can be used to land kill shot against high health MECs or Sectopod.
Movement PCS work well if you plan to use the Reaper strictly as a low health assassin. Combined with a superior sight and the Needle ability the Reaper can reliably sit in the middle of battles waiting for enemy units to be weakened then move into flanking positions to finish them off.
If the Reaper gets Shredder as one of its XCOM abilities, it can combo with Needle, bypassing and shedding armor at the same time.
Thanks to its unique form of stealth, it is very easy to use a one reaper squad to deal with any mission requiring interaction with an objective and evacuating, such as Alien Facility missions.
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NOTE:This article or section is in need of cleanup or verification. You can help the XCOM Wiki by improving it. Reason: 1. Group ability-related notes under individual bullets, e.g. "Shadow Concealment", "Claymore", etc., instead of listing them separately though one after another.