"You gotta eat something you're just skin and bones! Actually, you're just bones!"
Sam Stone[src]

The Kleer Skeleton (Kleer Knight in Serious Sam: Next Encounter) is an enemy that has appeared in every Serious Sam game except Serious Sam Advance. They are one of the most common and dangerous creatures in Mental's Horde.


The Kleer is the reanimated skeleton of an extinct race of creatures from the planet Kleer, of Alpha Canis Majoris. They existed peacefully until Mental dropped ten billion gallons of napalm on their planet, effectively wiping out the entire population.


Kleers appear somewhat equinus, but only in stature, as their physical properties are very different. They have large sharp horns on their heads, a long tail, scythe-like claws at the ends of their forearms, and hooves on their two hind legs; the sound of their hooves is a telltale sign of a Kleer.

It is worth noting that their appearance changes in most games:

  • In Serious Sam 1, Kleer Skeletons appear light brown in color, also sporting pauldrons around their shoulders. This appearance remains true in the HD and VR remakes, with the exception of the eyes, which glow yellow.
  • In Serious Sam 2, the appearance of Kleers is the same in color and shape, but they have more horned protrusions from the shoulders and skull, along with glowing yellow eyes. When they are killed, they make a bowling ball sound effect.
  • In Serious Sam 3: BFE, Serious Sam 3 VR: BFE and Serious Sam VR: The Last Hope, Kleer Skeletons look very different than their previous appearances. Their skeletal structure is more or less the same although the entire skull appears much larger. An additional third horn now protrudes from the forehead while their other horns appear more rounded, like a Sirian Werebull. This rendition also lacks the shoulder pauldrons seen in previous appearances. Kleers also have reddish glowing eyes in this installment. The skeleton color is also much darker, but the bones themselves appear scorched, a possible reference to their initial demise on their planet.


In most of their appearances, Kleers are often spawned in large numbers, or as traps in smaller numbers. They can be encountered with a group of any size, from lone ones ambushing behind corners or triggered by traps to swarms in open areas. In Serious Sam 2, Kleers are less prevalent, starting to appear on the planet Kleer.

In Serious Sam 3, they first appear as an enemy in Summer in Cairo (much like in other Serious Sam games, in that they always appear in the first level of every game). As Sam approaches the museum, one of the windows shatters, and a Kleer pops out and growls at Sam, which then charges towards him. After Sam kills it, three more Kleers break through more windows. In the next few levels, Kleers are one of the standard common enemies, appearing in hordes that consist of many hundred Kleers, especially in later levels, such as The Dark Bride and The Guardian of Time.

Behavior and skillsEdit

The resurrected skeleton of a Kleer is held together with magical links, giving them more resilence than a human or Gnaar. The magical links, however, are not overall that strong; a powerful blow wlll shatter the skeleton into pieces. Despite their seemingly frail structure, their speed and leaping ability is not to be underestimated. It is impossible to outrun a Kleer, even with the sprinting mechanic in Serious Sam 3.

Like most other creatures in Mental's army, Kleers will usually charge straight towards the target, though sometimes they will attempt to the flank the player in some games when the player places their crosshairs on them. At close range, Kleers will use their scythe-like claws to slash the target repeatedly, which deals low-moderate damage. They will also use their claws with their leap attack from medium range, which deals much more damage. They can use their claws to cling to walls, as seen in Serious Sam 3.

When a Kleer spots the player from medium to far range, they will conjure twin chainballs one after another in a single direction towards the player. These chainballs are low-grade, non-tracking projectiles, but cannot be destroyed until they hit an object or travel a certain long distance. However, due to their large size it's easy for them to hit small objects or other enemies in the way. Kleers are immune to chainballs conjured by other Kleers. On Serious difficulty in the Serious Sam Fusion version of Serious Sam 3, Kleers have a chance to conjure chainballs that travel horizontally which deal more damage than the regular chainballs.



  • While a single Kleer is barely a threat, they very rarely come alone aside those ambushing behind corners or triggered as a trap. Most Kleers appear in large groups in all their appearances and this is why they are dangerous.
  • A group of Kleers will attempt to mob the player and hurl chainballs from afar. When there is a large group of Kleers, the number of chainball projectiles can be very high and extremely difficult to dodge.
  • Against lone to small groups of Kleer Skeletons, the quickest way to kill them is by using the Double Barrel Coach Gun when they attempt to leap at the player. At such a close range it's hard to miss and the resulting shot will kill one instantly when timed right (the closer the better). This method is recommended when faced with a lack of room to dodge the Kleers' attacks.
  • Like Gnaars, damaging a Kleer quickly can cause them to flinch, which can give the player some time to keep their distance before finishing them off.
  • The XM214-A Minigun is extremely effective against hordes of Kleers. The rapid fire and damage output from the minigun can decimate an entire group in seconds, so long as the player can dodge their projectiles and does not get swarmed at the same time.
  • With large masses of Kleers, the SBC Cannon can effectively wipe all of them out if they are chasing towards the player in a straight line.
  • When a Kleer attempts to leap, it is easy to sidestep the attack, after which the Kleer will be momentarily stunned. However, large groups are difficult to deal with and it's easy to lose track of the Kleer that the player dodged, allowing them to surround and attack the player from all angles. Avoid allowing them to use their leap attack if possible.
  • Jumping while sidestepping increases the player's chances of dodging multiple simultaneous attacks. Sometimes, when a Kleer is close to the player but hasn't leaped at them yet, they might turn and run sideways to dodge the player's attacks and surround him/her if they put their crosshairs on them, so when facing huge hordes, try to size them down at range with explosive weapons as much as possible.
  • When appearing with other enemies, Kleer Skeletons should be medium-priority targets but higher if they get closer to melee range and there are many of them. Their melee attacks are rather powerful, but they can be dodged with some skill and ranged attacks can be dodged as well with relative ease unless there are a lot of Kleers.
  • Kleers appearing with other melee enemies are more dangerous as other enemies tend to shield Kleers and often make their movement and especially leap trajectories less predictable.

Serious Sam 1Edit

  • When in a larger room, the Military Knife is a faster way to take a group out. Before the Kleer(s) reach the player, a few shots from the Schofield .45 can be used to weaken them enough to be taken out with a single knife attack. The shotgun is not practical for large groups due to its slow rate of fire as the next Kleer will attack before the gun is ready to fire again.
  • When dealing with large groups, explosives (especially grenades) are an effective way to take out Kleers at long to mid range. The minigun and XL2 Lasergun (or the Thompson submachine gun if the previous two weapons are unavailable) are good for mid to close range encounters to compensate for the fact that using explosives at such close ranges will typically incur self-damage.
  • In The Second Encounter, at close range, the XOP Flamethrower is extremely effective against groups of Kleers of any size. A single flame puff can damage several skeletons, it does decent damage per minute, has plenty of ammunition and an after-burn effect. The chainsaw is also effective with Serious Damage.

Serious Sam 2Edit

  • Kleer Skeletons pose much less of a threat in the second installment despite the slower player walking speed in this game. Firstly, Kleers are significantly slower as well than in the previous installments. Secondly, the Double Shotgun is much stronger and can take out Kleer Skeletons with one shot even at longer range. The Auto Shotgun is also capable of killing a Kleer Skeleton with two shots even at mid to far range.
  • Against larger groups, the XL 808 Plasma Rifle and XM214-A Minigun are an alternative option.
  • For extremely large groups, explosive weapons are a good option so long as the Kleers are far away.

Serious Sam 3: BFEEdit

  • It is harder to dodge Kleers in this installment due to their faster leap attack speed. The Sledgehammer can kill a Kleer with one swing and is faster than the double shotgun. However, the attack is delayed so it must be more well-timed.
  • In Serious Sam 3, rough terrain is also susceptible to make the Kleer's movement less predictable.
  • In this installment, Kleers are medium-high priority targets due to the player's slower movement speed, even when sprinting.
  • The Sirian Mutilator works well against smaller groups of Kleers. In addition, the Mutilator briefly stuns them as well.
  • The player can attack Kleers with a special Melee Grab finishing move only when they are charging at the player or leaping. Sam will sidestep and put the Kleer in a headlock and promptly pull the Kleer's head off. The head can then be thrown as a weapon, doing minor damage. The range of the melee grab is larger than the Kleer's own attack range, so with good timing the player can easily avoid damage. As with all melee grabs, this attack takes a short amount of time and immobilizes Sam for the duration, making it impractical for groups of Kleers but is effective against lone or a few Kleers.
  • Like in the previous games, the minigun makes a great anti-Kleer weapon. However, minigun ammo is much scarcer in the campaign, so the player needs to be aware of this if they don't have enough ammunition to face of an entire horde.
  • Against larger groups, rockets and the AS-24 Devastator are good for killing Kleer Skeletons at medium to medium-long distances as Kleers generally run straight towards the player when spotted. C-4 Demolition Charges are very useful against denser groups that are seen approaching beforehand. When Kleers from a large group get a bit too close and are starting to leap behind the player, it is best to switch to the lasergun and minigun to not cause self-damage from explosives.
  • Large hordes of Kleers can be dealt with the cannon or the Devastator, but using the cannon may deplete ammunition quickly.

Serious Sam: Double DEdit

  • The 12 Gauge Shotgun is effective against lone or small groups of Kleers, as a close range shot can kill one instantly.
  • Unlike other games, Kleers don't have a ranged attack. This makes them harmless at long range.
  • Against larger groups, a Gunstack combination of both Thompson submachine gun and XL4 Lasergun works well against them.

Serious Sam: The Random EncounterEdit

  • The Kleer's projectiles can be avoided by moving up or down.
  • The minigun is useful against small to medium groups of Kleers.
  • The rocket launcher is effective against larger groups of Kleers.

Serious Sam: The Greek EncounterEdit

  • The pump-shotgun is effective against lone Kleers, as two shots at close range is enough to kill each one.
  • The minigun is effective against larger groups, due to its rapid rate of fire and high damage.

Serious Sam's Bogus DetourEdit

  • Groups of Kleers can be easily killed with the Auto Shotgun, pump shotgun, Thompson or the laser cannon.
  • The minigun can easily take out medium to large-sized groups of Kleers.
  • The Devastator, Erasergun or cannon are the best weapons to use against Kleers when they are lined up or clustered together.

I Hate Running BackwardsEdit

  • The best way to deal with Kleers is to use melee attacks frequently. A well placed melee attack, especially when upgraded with Super Swinger, can effectively take out a pack of Kleers with relative ease.
  • Alternatively, a simple secondary weapon such as the Shotgun is enough to deal with smaller Kleer threats.

Behind the scenesEdit

  • Kleers in Test 1 looked like Egyptian mummies, though they had the same animations as they have in Serious Sam 1.

Related achievementsEdit

Serious Sam HD: The Second EncounterEdit

Bone crusher Bone Crusher
Kill 300 Kleers with the Cannon.

Serious Sam 3: BFEEdit

Kleer wrestler Kleer Wrestler B
Tear off 10 Kleer heads.
Bfebone crusher Bone Crusher (5G) B
Smash 20 Kleers with the Sledgehammer.

Serious Sam FusionEdit

Kleer Wrestler Kleer Wrestler
Tear off 10 Kleer heads.
Bone Crusher SSF2017 Bone Crusher
Smash 20 Kleers with the Sledgehammer.
Crunchy Crunchy
Kill 100 Kleers with the Cannon.

Serious Sam 3 VR: BFEEdit

Bone Crusher Bone Crusher
Smash 20 Kleers with the Sledgehammer.


  • In both the First Encounter and Second Encounter, the player can select the Kleer as their multiplayer model. It is the first enemy model and the only one still appearing in the HD and VR remakes.
  • Like the Scythian Witch-Harpy, Kleers have a death animation in Serious Sam 1, but not in Serious Sam HD and Serious Sam VR.
  • The Kleers are similar to the Fiend enemy from the Quake series, both in design and behavior.
  • Kleers in Serious Sam 3 can scale down walls, clinging to them like Antaresian Spiders, unlike Kleers from previous games.
  • In Serious Sam 3, you can attach two C-4 to a Kleer — one on its head and one on its chest.



Serious Sam 1Edit



Serious Sam: Next EncounterEdit

Serious Sam 2Edit

Serious Sam 3: BFEEdit

Serious Sam VR: The Last HopeEdit

Serious Sam: Double DEdit

Serious Sam: The Random EncounterEdit

Serious Sam: The Greek EncounterEdit

Serious Sam's Bogus DetourEdit

I Hate Running BackwardsEdit

Serious Sam 4: Planet BadassEdit

List of appearancesEdit

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