Cumulonimbus is the boss of the Cloudy Temple, which is a structure from the Legendary Monsters mod that generates in the mountain biomes of the Overworld. You will find Cumulonimbus asleep in the middle of the temple’s arena, he won’t wake up until a player gets within 8 blocks of him. He has 350 health, which equates to 175 hearts, and there’s two phases to get through.
Defeating Cumulonimbus is the only way to get an 
Air Rune, which is needed to craft the 
Wand Of Clouds and the 
Axe Of Lightning. He’ll also drop a pair of 
Atmospheric Boots every single time, so there’s no luck involved with the loot. Most of the fight has to be up close, as he ignores damage while his target is more than 15 blocks away.
Location
Cumulonimbus only exists inside the Cloudy Temple, he can’t be found anywhere else in the world. The Cloudy Temple generates on the surface in mountain biomes, and the temples are spaced around 70 chunks apart, which works out at roughly 1,100 blocks. If cheats are enabled, the command below can be used to get the coordinates of the nearest one.
Without cheats, you’ll want to craft an 
Eye Of Air, which is made from 4 
Feathers placed around an 
Ender Pearl. Feathers come off any Chicken, so the Eye is cheap to make before you head up into the mountains.
Throw it like an 
Eye of Ender and follow it toward the nearest Cloudy Temple, within about 100 chunks. About one throw in five it shatters instead of dropping back down, so craft a few before setting off.
The Cloudy Temple is built out of 
Polished Diorite and 
Glass, so it’s quite easy to spot against the side of a mountain. Cumulonimbus sits in the arena at the center of it, with the rest of the rooms branching off from there. Two Hovering Hurricanes stand lower down in the same part of the temple, so deal with those before you wake him.
Behavior
Cumulonimbus starts out asleep, and he can’t be damaged at all while he is sleeping. Once a player comes within 8 blocks he will wake up, which is also when the boss bar appears on screen. He’ll target players first, but he will also go after 
Iron Golems and 
Snow Golems. They won’t last long if you were planning to use them as a distraction.
Attacks
Most of the attacks that Cumulonimbus uses are smashes and slams with his arms, which hit everything in front of him. The heavier ones add a small percentage of your maximum health on top of the listed damage, so extra hearts won’t help as much as you might expect. If you’re blocking with a 
Shield when one of these lands, then the Shield can be disabled for a few seconds.
| Attack | Phase | Damage | What to Know |
|---|---|---|---|
| Ground Smash | 1 and 2 | 19.5 | Used when you’re within 5 blocks, and it disables a raised Shield for 2.5 seconds |
| Cloud Ring | 1 | 7 per cloud | Rings of clouds form above him and burst, used when you’re within 7 blocks |
| Cloud Trail | 1 | 8 per cloud | A line of clouds bursts just above your head, used from 7 to 18 blocks away |
| Tornado | 1 and 2 | 7 | Thrown at you from 6 to 13 blocks away |
| Flying Slam | 1 and 2 | 25 + 8% of your max health | Hits all the way around him for 6.5 blocks, and disables a raised Shield for 7 seconds |
| Charge | 1 and 2 | 22 + 3% of your max health | Stuns you for almost 3 seconds, with an 11 second cooldown |
| Smash Combo | 2 | 18, then 19 | Two smashes with sparks of electricity in between |
| Triple Slam | 2 | 16, 16, then 18 | Three slams in a row |
| Electric Stomp | 2 | 7 per spark | Two stomps that send electricity along the ground |
| Lightning Laser | 2 | 5 + 1% of your max health per hit | A beam that lasts around 4 seconds, no more than once every 25 seconds |
The Charge and the Flying Slam are the two to watch for, as they take control away from you. Being Stunned by the Charge leaves you stuck in place for almost 3 seconds.
You won’t be able to block, eat or use items until it wears off. Both of these can be sidestepped, which is better than trying to block them, as they also disable a Shield for the longest.
Phases
The fight is split into two phases, and the change happens once Cumulonimbus drops below 65% health, which is around 227 health. He will stop attacking, throw out a burst of Tornadoes and knock back everything around him. He can’t be damaged until the change has finished. If everyone leaves and he heals back above 65%, then he’s able to reset to the first phase again.
First Phase
Above 65% health
In the first phase, Cumulonimbus relies on his clouds, which he’ll either summon in rings above himself or send in a line toward you. These burst a moment after they appear, so you’ll want to keep moving rather than standing still underneath them. 
Arrows work as normal during this phase, which makes it the best time to use a 
Bow if you’ve brought one.
Second Phase
Below 65% / 227 health
The second phase adds electricity to most of his attacks, along with the Lightning Laser, which he can fire once every 25 seconds or so. After the laser ends, Cumulonimbus will lose consciousness and drop to the floor, where he’ll stay for around 3 and a half seconds. This is the safest opening in the whole fight, so it’s worth saving your hits for it.
Arrows are limited in this phase as well, as only one of them can damage him every 1.5 seconds. Once Cumulonimbus is below 25% health, a Charge that misses will be followed by a second Charge straight away. Don’t relax after dodging the first one, as the second one follows about a second later.
Special Mechanics
Cumulonimbus has a damage cap, so no single hit can deal more than 18 damage to him, whichever weapon you’re using. After each hit he’s immune for half a second, and any hit within 1.5 seconds of the previous one only deals half damage. So steady hits about a second and a half apart do far more than spam clicking, and there’s no quick way to finish him.
Any damage is ignored while the player he’s targeting is more than 15 blocks away, so shooting Cumulonimbus from a distance does nothing. He will also break the blocks around himself after every couple of hits, as long as mob griefing is turned on. It stops him from being trapped inside a box.
Cumulonimbus is immune to quite a lot of damage types as well. Fire, Lava, fall damage, drowning, freezing, lightning and explosions won’t hurt him, and he can’t be knocked back. Potion effects like Poison or Slowness can’t be applied to him at all, and Splash Potions are ignored completely, so it isn’t worth bringing any Potions of Harming.
Cracking Cumulonimbus With an Axe
There’s one more mechanic which is easy to miss, as it only applies while Cumulonimbus is using his Ground Smash or his Smash Combo. During these attacks, any hit that would deal more than 5 damage gets cut down to 4. You might notice your hits doing very little here, even with a good weapon.
To get around this, you’ll need to hit him with a fully charged Axe swing during those attacks. After 3 of these his body will visibly crack, with a sound like a wooden door being broken. From then on, hits during those two attacks deal their full damage again, up to the usual cap of 18.
The crack lasts for the rest of the fight, so it’s worth doing early on. Any type of Axe can be used for this, as it’s the fully charged swing that counts, rather than how much damage the Axe does.
Eating, Resistance and Healing
Cumulonimbus will interrupt you if you’re eating when one of his melee attacks lands, and the food is put on a short cooldown afterward. On top of this, any Resistance effect of level III or higher is knocked down to level I by the same hit. It means 
Golden Apples have to be eaten at a distance, and that stacking Resistance from other mods won’t carry you through.
If he is left without a target for 3 seconds, Cumulonimbus will begin to heal, and it’s fast. He can go from almost nothing back to full health in under 15 seconds. A failed attempt will usually mean starting again from the first phase, so it’s better to retreat only when you really have to.
Drops
Cumulonimbus will always drop 1 Air Rune and 1 pair of Atmospheric Boots, along with 100 experience. Both drops are guaranteed, so Looting doesn’t make any difference here. The Air Rune is the important one, as it’s a crafting ingredient which can’t be obtained in any other way.
Cumulonimbus Drops
Air Rune 
Atmospheric Boots An Air Rune can be turned into either a Wand Of Clouds or an Axe Of Lightning. The Wand Of Clouds needs a 
Cloud Rod as well, which can be obtained from the Hovering Hurricanes around the temple. They drop between 1 and 3 at a time. As you only get one Air Rune per fight, you’ll have to pick between the two weapons.
Atmospheric Boots do have a crafting recipe which uses an Air Rune, but Cumulonimbus drops a pair anyway, so it would be a waste of the rune. Cumulonimbus also can’t be summoned a second time, as the 
Teleport Machine is only used for The Obliterator. If you want both the Wand Of Clouds and the Axe Of Lightning, then a second Cloudy Temple will need to be found.
Strategy
Any weapon that reaches 18 damage is as good as any other here, as nothing above the cap counts, so a Sword with Sharpness is plenty. Keep an Axe on your hotbar too, it’s needed to crack him during his Ground Smash. For armor, full Diamond or Netherite with Protection IV is what to aim for, as his bigger attacks deal over 20 damage before armor.
During the fight, try to stay within about 10 blocks of Cumulonimbus, as your damage stops counting once you’re more than 15 blocks away. Sidestep the Charge rather than backing away from it, then use the gap afterward to get a couple of hits in. Any time you need to eat, get some distance from him first, as being hit will cancel it.
In the second phase, the whole fight should be built around the Lightning Laser. Keep moving sideways while the beam is firing, as it deals damage in lots of small hits that add up quickly. Then run in as soon as Cumulonimbus drops to the floor, you’ll get around 3 and a half seconds to attack him before he’s back on his feet.
FAQ
Cumulonimbus is found sleeping in the arena of the Cloudy Temple, which generates in mountain biomes like Meadows, Groves, Cherry Groves and Jagged Peaks. The easiest way to track one down is to throw an Eye Of Air and follow it, just like an Eye of Ender. With cheats enabled, the /locate structure legendary_monsters:cloudy_temple command will give you the coordinates instead.
The Air Rune is a crafting ingredient, and it can be used to make the Wand Of Clouds, the Axe Of Lightning or a pair of Atmospheric Boots. Cumulonimbus drops exactly one each time he’s defeated. He drops the boots as well, so the Air Rune is best spent on one of the two weapons.
Stay close, as damage doesn’t count when you’re more than 15 blocks away, and space your hits out, because each one is capped at 18 and anything within 1.5 seconds of the last is halved. Dodge the Charge and the Flying Slam instead of blocking them. In the second phase, wait out the Lightning Laser, as he collapses for a few seconds afterward and that’s the best time to attack.
There isn’t a way to summon Cumulonimbus again in survival, as the Teleport Machine and the 
Eye Crystal are only used to summon The Obliterator. Each Cloudy Temple has one Cumulonimbus sleeping inside it, so you’ll need to find another temple for a second fight. Throwing another Eye Of Air from a different area is the quickest way of doing that.
