Mutations were introduced to the site on April 12th 2014 within this news post. What mutations were added in during that update are not detailed, however the very first mutated lion was hinted at two days later in this news post.

It is mentioned within the first news post that "the more severe the mutation, the more chance it may prove fatal for the cub or affect gameplay in some way". Lethal mutations, as the name suggests, are mutations that will impact your lion's life to the point that they die at an early age. These mutations are incredibly rare, and the majority of them will kill a lion before they reach adolescence. These mutations are all visible from birth as well, so you'll instantly know if something's wrong with your little cub. Let's see what some of these mutations are!

The following lethal mutations are ones that only affect cubs.

Cleft Palate  

Cleft Palate is a lethal mutation where your cub has a split in their lip and roof of their mouth, causing them to have trouble with nursing.
Cleft Palate cubs will pass away on the rollover that they turn 3 months old.

Cleft Palate Health Messages
Age	Content
0 Months	Oh no! This cub has been born with a facial defect - a cleft lip! Its snout is split heavily, and Cub has trouble with breathing.
1 Month	Cub is trying to drink milk. Sadly, a lot of it spills around.
2 Months	Due to issues with suckling, Cub became malnourished.
3 Months	Unable to properly feed, Cub passed away due to health complications.

Conjoined Cubs  

Conjoined Cubs is a lethal mutation where your cub is actually two cubs joined together, as the name suggests; however, gameplay-wise, they are still considered to be one lion.
Conjoined Cubs will pass away on the rollover that they turn 2 months old.

Conjoined Health Messages
Age	Content
0 Months	Your lioness notices her Cub… Is two cubs, joined together at vital places! She isn't sure if they are one cub or two. It… They both suck the milk though, but don't move much.
1 Month	While cubs this age learn how to walk and meet the world around them, Cub are having trouble functioning and struggle to move. They constantly trip and get into trouble.
2 Months	Cub died last night due to the lethal condition of the bodies.

Cyclopia  

Cyclopia is a lethal mutation where your cub has one large eye, rather than two. Their eye leaves no room for their nose, which complicates their breathing.
Cyclopia cubs will pass away on the rollover that they turn 1 month old.

Cyclopia Health Messages
Age	Content
0 Months	Your lioness notices her Cub is different to all the others. It doesn't move, barely breathes, and its muzzle… It's just causing her heart to shatter.
1 Month	Cub died last night due to being lethally deformed.

Extra Limbs  

Extra Limbs is a lethal mutation where your cub has seven (visible) legs, rather than the standard four.
Extra Limbs cubs will pass away on the rollover that they turn 6 months old.

Extra Limbs Health Messages
Age	Content
0 Months	Your lioness notices her cub is different to all the others. She can't even count all the little legs! She's very worried but the cub curls up and suckles milk nicely.
1 Month	As cubs at this age learn to walk and wiggle around, poor Cub just drags its body and squeaks sadly. The appetite isn't as great either.
2 Months	Cub has trouble following its mom around. It often gets left behind and prefers to hide in the bush.
3 Months	Cub sometimes plays in the den, but sleeps most of the day, looking sad while its mom nudges it to be more active.
4 Months	The multiple legs of Cub prevent it from developing muscles correctly. Shaky limbs won't let it play too long and its general health is noticeably declining.
5 Months	Apathy of Cub is preventing the cub from moving or eating much.
6 Months	Cub died last night due to being lethally deformed.

Harlequin Ichtyosis  

Harlequin Ichtyosis is a lethal mutation where your cub has a thick, cracked skin coating its body, rather than fur. This is the only lethal mutation that makes all cubs with this mutation look identical.
Harlequin Ichtyosis cubs will pass away on the rollover that they turn 1 month old.

Harlequin Ichtyosis Health Messages
Age	Content
0 Months	Looks like Cub was born with a skin thick like a shell. It has trouble breathing and suckling.
1 Month	Cub died due to breathing complications.

Lipomatosis  

Lipomatosis is a lethal mutation where your cub is covered in lumpy, fatty tumours.
Lipomatosis cubs will pass away on the rollover that they turn 5 months old.

Lipomatosis Health Messages
Age	Content
0 Months	Your lioness gave birth to Cub, and notices it is different to all the others. It has lumps all over its tiny body, but appears healthy otherwise.
1 Month	The lumps covering Cub's body are getting bigger…
2 Months	Cub has trouble moving. Looks like some lumps are growing deeper inside of the little cub's body as well.
3 Months	Cub no longer plays with other cubs, having all its energy drained by trying to stand up or walk with all that weight.
4 Months	You notice lumps covering Cub's spine and back. The cub doesn't move very much lately and is very apathetic.
5 Months	Cub passed away due to health complications.

Sirenomelia  

Sirenomelia is a lethal mutation where your cub's back legs are fused together.
Sirenomelia cubs will pass away on the rollover that they turn 5 months old.

Sirenomelia Health Messages
Age	Content
0 Months	Your lioness gave birth to Cub, a slightly deformed baby. She's unsure if it will survive but it seems to crawl for milk like all others.
1 Month	Cub crawls around using its front legs only. The merged hind legs don't seem to bother it, and it seems to be able to poop just fine.
2 Months	Other cubs this age prance around, but Cub just paws at nearby insects, making it a bit of an outcast.
3 Months	Cub's mom is worried for it - it does not seem to grow much lately.
4 Months	Cub has trouble digesting and hasn't been eating much in the past few days. It meows quietly from pain.
5 Months	Cub passed away due to health complications.

Two Heads  

Two Heads is a lethal mutation where your cub has two heads that are fused into one; however, gameplay-wise, they are still considered to be one lion.
Two Heads cubs will pass away on the rollover that they turn 3 months old.

Two Heads Health Messages
Age	Content
0 Months	Your lioness notices her Cub is different to all the others. It has two mouths, two noses, and four eyes! She's scared for its life but the cub suckles milk from both mouths.
1 Month	Cub seems to be learning how to walk and play properly, although it is very apathetic and prefers to sit and look around with its widened field of view.
2 Months	Cub has trouble feeding and controlling its body. It had a seizure last night.
3 Months	Cub died last night due to lethally deformed head.

The following lethal mutations are ones that can affect a lion from the newborn stage to adult stage.

Deaf  

Deaf is a lethal mutation where your lion lacks the power of hearing. It is also the only lethal mutation that does not change the way a lion looks; however, it does change many mechanisms connected to lions. Deaf lions cannot hunt, patrol, or be a king. If a deaf lioness is pregnant, she can die while pregnant; a deaf nursing lioness, however, cannot die while nursing.
What's also unique about Deaf lions is that they give updates about your lion's health, as well as unique flavour texts specific to the Deaf mutation!
Deaf lions can die randomly between 4 months to 4 years of age. If they live to be 4 years old, they will pass away upon the next rollover.

Cub Newborn Cub Young Cub Adolescent Female Adolescent Male Adult Female Adult Male

If your lioness gives birth to a cub with the Deaf mutation, you will receive the following birth message.

As your Deaf lion ages, you will receive occasional updates about their life with a lethal mutation. These messages will only occur if your lion is 3 years or older.

If you visit your Deaf lion's den page, you may receive some unique flavour texts that are specific to the Deaf mutation!

Sadly, once it's your Deaf lion's time, you will receive one of the following messages upon their passing.

If you're looking to breed for lethal mutations, or your perfect breeding project cub was born with a lethal mutation, these items may be of some assistance to you.

Before Breeding

It's ideal to give these items to your chosen lioness before breeding her, as using a GMO Cow, Lion Meat, or Lion Scrotum on an already-pregnant lioness will not affect the litter she's currently carrying - she must be given the item before her breeding in order for them to affect her next immediate litter. In regards to Cotton Root Barks, it's advised to use them on a dud breeding, then breed her to your preferred stud once she's back into heat after miscarrying.

Cotton Root Bark This herb will induce a miscarriage on any pregnant lioness. The lioness will come back into heat again in 3 days. Her mutation chance will increase, as well as the lethality of the mutation. Purchased from the Oasis for 1 GB.

GMO Cow In response to locust plaguing the crops, humans created genetically modified cattle. Who knows what will happen to lioness's next litter if she eats some of this meat! - [next breeding, high chance of mutated cub but not 100%] Purchased from September's Prophet Shop for 150 JB.

Lion Meat Cannibalism is unnatural enough to cause your lioness's next breeding to have a low chance to result with a mutated cub. (Chance is much greater than 1% fertility would have, but lower than GMO cow). Purchased from January's Boneyard for 100 LB, January's Carrion Shop for 2000 SB, or the Gorilla Enclave for 300 MT.

Lion Scrotum When given to female, her mutation has 25% chance to pass in next breeding as long as it has no extraneous requirements. This effect triggers last if bred cub still has no mutation. Uses GMO/LM slot. (Hybrids excluded) Purchased from February's Slap Shop for 80 HS or May's Champion Shop for 400 MB.

Removing A Mutation

As mentioned previously, although it's incredibly rare, you can breed a gorgeous cub that happens to have a lethal mutation. If you wish to remove its mutation, you must purchase the following item.**

Safou Fruit Ancient lion medicine for removing bad genetic mutations from the body. Purchased from Monkey Business for 1000 SB.

Preserving A Mutation

As lethally-mutated lions die much earlier than healthy lions, you may be worried about losing your beloved mutated cub (or lion). To preserve your lion in their current state, these items will help you.

Jellyfish This item will freeze a chosen cub forever in time. It will never age, cub train, get hungry, or lose mood. You have up to one hour after freezing to reverse its effects (the item will be refunded). Won as a jackpot prize from Slots.

Turritopsis Jellyfish This item will freeze a chosen adolescent or adult lion forever in time. It will never age, breed, get hungry, hunt, lose mood, or patrol. You have up to one hour after freezing to reverse its effects (the item will be refunded). Purchased from the Oasis for 5 GB.

Q: Can I remove a mutation from my lion?
A: Yes. If a lion is born and you do not wish for it to have a mutation, or you want to save a lethally-mutated lion before it passes away, you must use a Safou Fruit. They can be bought for 1000 SB from Monkey Business.

Q: I had a lethal mutation born! How can I prevent it from dying?
A: You can either use a Safou Fruit to remove its mutation, or give your cub a Jellyfish. Jellyfish are given out as a rare jackpot prize from the Slot Machine game on Lioden. Note that if you wish to use a Jellyfish to preserve your lethal cub, you will need to have available frozen slots.

If you're wanting to freeze an adolescent or adult lethal lion, you will need a Turritopsis Jellyfish, which can be bought for 5 GB from the Oasis. You will need an available frozen slot in order to use a Turritopsis Jellyfish as well.

Q: Is there any way to pass on a lethal mutation?
A: Only for the Deaf mutation. All other lethal mutations are specific to cubs. As cubs cannot breed, they cannot be passed down to offspring. As for the Deaf mutation, you can give an adult Deaf lioness a Lion Scrotum, which will give her a 25% chance per cub to pass down her mutation.

Q: Who was the first lethally-mutated lion on the site?
A: Chernobyl the Extra Limbs cub! They are memorialised within their owner's Pride Dynasty. Chernobyl was born on April 26th 2014, 28 years after the actual Chernobyl incident occurred—what strange timing!

Q: Some of the lethal mutation art really upsets me. Is there any way I can request that my account be blocked from breeding certain mutations?
A: No. Accounts cannot be blocked from breeding mutations. Unfortunately, the only way to avoid these images are to block them using external add-ons or programs. If you wish to block an image from your browser, we recommend utilising this guide: https://kb.iu.edu/d/acpv

Q: Are any lethal mutations gender-specific?
A: No. Lethal mutations can occur on both male and female cubs. This means that you can safely sex change a lethally-mutated cub or adolescent without them losing their mutation.

Q: Can my lethally-mutated lion die before its time?
A: Yes. If you do not assign your lethal cub to a broodmother, it can die earlier than its scheduled passing age. Note that assigning a lethal cub to a broodmother only prevents it from deaths attributed to low cub survival rates - it does not stop a Cyclopia cub from dying at 1 month old, or a Deaf cub from randomly dying.

Q: Can my Deaf lion become king?
A: No. Deaf lions cannot hunt, patrol, or be kinged. They can become broodmothers and protect cubs, however.

Q: Can my Deaf lioness die while nursing cubs?
A: No. If a Deaf lioness is nursing, her chance of death is halted until her cubs wean at 5 months of age.

Q: Can my Deaf lioness die while pregnant?
A: Yes. It is advised to use an Instant Cub Delivery on a pregnant Deaf lioness, as she is at risk of dying even while pregnant.

Q: Is there any way to increase my chances of producing a lethal mutation?
A: Yes. Generally, lower fertility lionesses have a naturally higher chance of producing lethal mutations than higher fertility lionesses; however, this natural chance is extremely low. Your best odds would be to breed with your lioness, then give her a Cotton Root Bark to induce a miscarriage. Doing this will increase her general odds of producing a mutated cub, as well as increase the lethality chance of that mutation.

You can use GMO Cows and Lion Meat as well, though they have a higher chance of producing any average mutation, not lethal mutations specifically. It is advised to only use Cotton Root Barks, as they are the cheapest method to producing mutations, but some players have had luck combining Cotton Root Barks and GMO Cows.