"That one's for Jones, bones."

The Kleer, also known as the Kleer Skeleton, 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 hordes.


Kleers themselves were once a species indigenous to the planet Kleer, of Alpha Canis Majoris. They existed until Mental dropped ten billion gallons of napalm on their planet, effectively wiping out the entire population. The Kleers were resurrected as skeletons, with their bones held together by magical links. Despite their seemingly frail structure, their speed and leaping ability is not to be underestimated.

In most of their appearances, Kleers are often spawned in large numbers, or as traps in smaller numbers. They are occasionally accompanied by other enemies, such as ScrapjacksGnaarsBeheaded Kamikazes, Major or Minor Bio-mechanoids.


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, sharp scythe-like claws at the ends of their forearms, and hooves on their two hind legs. The resurrected skeleton is held together with magic. Although more resilient than a human or Gnaar, the strength of the magical bonding is still weak; a powerful blow will shatter the skeleton into pieces.

It is worth noting that their appearance changes in each game. In Serious Sam 1, Kleer skeletons appear light brown in color, also sporting pauldrons around their shoulders. This appearance remains true in the HD 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, 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.

NETRICSA descriptionEdit

"An undead skeleton of a being from an extinct race from the planet Kleer, of Alpha Canis Majoris. Long sharp claws can inflict significant damage with each hit. Their dangerous jumping attacks are best evaded by sidestepping quickly. The sound of its hooves running is a tell-tale sign of an incoming Kleer. Bones of undead Kleers are connected by relatively weak magical links. A powerful blow will shatter the skeleton into pieces."


Kleer skeletons are one of the basic and most common enemies in the Serious Sam series. 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, Kleer skeletons are less prevalent, starting to appear on the planet Kleer.

In Serious Sam 3, a Kleer's skull can be seen half-buried in the desert during the opening cutscene, surrounded by flies. They first appear as an enemy in Summer in Cairo (much like in other Serious Sam games, where they always appear in the first level of every game). As Sam approaches the museum, one of the museum windows shatters, and a Kleer pops out and growls at Sam, which then charges towards him. After Sam kills the beast, 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.


Kleer have a limited number of attacks.

  • A Kleer will use slash attacks at close range which do low-moderate damage.
  • When close enough, they can leap at Sam with great speed which does moderate damage.
  • When at a distance, they can conjure twin chainballs one after another in a single direction towards the target.

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.


  • 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 Serious Sam games and this is why they are dangerous.
  • Kleers are very fast — it is impossible to outrun a Kleer (even while sprinting in Serious Sam 3: BFE). A group of Kleers will attempt to mob Sam 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.
  • 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 you dodge, allowing them to surround and attack you from all angles. Avoid allowing them to use their leap attack if possible.
  • Jumping while sidestepping increases your chances of dodging multiple simultaneous attacks. Sometimes, when a Kleer is close to you but hasn't leaped at you yet, they might turn and run sideways to dodge your attacks and surround you if you put your crosshairs on them, so when facing huge hordes, try to size them down at range with explosives 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. In Serious Sam 3, they are medium-high priority targets due to the player's slower movement speed, even when sprinting.
  • 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. In Serious Sam 3, rough terrain is also susceptible to make the Kleer's movement less predictable.
  • 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.

Serious Sam 1Edit

  • When in a larger room, the Military Knife is a faster way to take a group out. Before the Kleers 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 Tommy 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 XM-214-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 shot and is faster than a double shotgun. However, the attack is delayed so it must be more well-timed. The Sirian Mutilator works well against smaller groups of Kleers. In addition, the Mutilator briefly stuns them as well.
  • You can attack Kleers with a special Melee Grab finishing move only when they are charging at you or leaping. Sam will sidestep and grab 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.
  • 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 is very useful against denser groups that are seen approaching beforehand. When Kleer 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 SBC Cannon or the AS-24 Devastator, but using the cannon may deplete ammunition quickly.

Related achievementsEdit

Serious Sam HD: The Second EncounterEdit

Bone crusher Bone Crusher
Kill 300 Kleers with the Cannon.

Serious Sam 3: BFEEdit

Bfebone crusher Bone Crusher
Smash 20 Kleers with the Sledgehammer.
Kung-fu fighter Kung-fu Fighter
Perform all possible finishing moves in the game.

Serious Sam Fusion 2017Edit

Crunchy Crunchy
Kill 100 Kleers with the Cannon.


  • In both the First Encounter and Second Encounter, the player can select the skeleton as their multiplayer model. It is the first enemy model and the only one still appearing in the HD remakes.
  • Kleers in Test 1 looked like Egyptian mummies, though they had the same animations as they have in Serious Sam 1.
  • The Kleers are similar to the Fiend enemy from Quake, 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: BFE, you can attach two C-4 to a Kleer — one on its head, and one on its chest.



Serious Sam 1Edit

Serious Sam 2Edit

Serious Sam 3: BFEEdit

Serious Sam's Bogus DetourEdit

Serious Sam: Double DEdit

Serious Sam: The Random EncounterEdit

List of appearancesEdit