Release date  22 September 2014 (Update) 

Members  Yes 
Quest  Plague's End 
Location  Prifddinas 
Examine  A crystal key can open it. 
The crystal key chest is a treasure chest located in Ivy Sophista's house in Taverley. A second chest is located in Prifddinas in the Iorwerth Clan district. The chests are locked and can only be opened by a crystal key. Attempting to open the chest without the crystal key yields the message: "This chest is securely locked shut." The crystal key is made up of a loop half of a key and a tooth half of a key; you can make the crystal key by using them with each other or selecting the "Assemble" option.
Opening a crystal chest grants a variety of rewards, which always include an uncut dragonstone. The crystal chest in Prifddinas grants slightly better rewards than the Taverley chest. The crystal key sells for more than most of the rewards, making it generally more profitable to sell the key than to use it. The key is used once and disappears upon usage.
Rewards possibilities
The chest loot always includes an uncut dragonstone, together with a random reward generated from 13 possible reward tables. Below are the values of the chest's contents, based on current Grand Exchange prices. Unless otherwise specified, all possibilities give all of the listed rewards when obtained.
After an update, wearing a ring of wealth will increase your chances of getting a better drop.
It is only possible to obtain rune platelegs if you are a male character, and a rune plateskirt if you are a female character.
Taverley chest
Possibility 1  Fruit tree seed
The expected value of Possibility 1 is 17,505, which is a profit/loss of 3,715 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Calquat tree seed  1  Common^{[1]}  256  
Papaya tree seed  1  Common^{[1]}  3,742  
Palm tree seed  1  Uncommon^{[1]}  40,104 
 ^ ^{a} ^{b} ^{c} With Possibility 1, you are guaranteed to get either a calquat tree seed, a papaya tree seed or a palm tree seed. Both the calquat and papaya tree seed have a probability of 5:11 (45.45%), and the palm tree seed has a probability of 1:11 (9%).
Possibility 2  Lantadyme seeds
The expected value of Possibility 2 is 13,570, which is a profit/loss of 7,650 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Lantadyme seed  2  Common  1,528 
Possibility 3  Grimy torstols
The expected value of Possibility 3 is 22,140, which is a profit/loss of 920 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Grimy torstol  2  Common  10,098 
Possibility 4  Runes
The expected value of Possibility 4 is 164,592, which is a profit/loss of 143,372 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Law rune  50  Common  27,650  
Chaos rune  50  Common  7,250  
Cosmic rune  50  Common  20,950  
Death rune  50  Common  10,450  
Nature rune  50  Common  21,250  
Body rune  200  Common  11,200  
Mind rune  200  Common  3,800  
Earth rune  200  Common  3,400  
Air rune  200  Common  17,800  
Water rune  200  Common  4,800  
Fire rune  200  Common  24,000 
Possibility 5  Iron ore
The expected value of Possibility 5 is 148,242, which is a profit/loss of 127,022 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Iron ore  200 (noted)  Common  136,200 
Possibility 6  Coal
The expected value of Possibility 6 is 27,342, which is a profit/loss of 6,122 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Coal  150 (noted)  Common  15,300 
Possibility 7  Rune bars
The expected value of Possibility 7 is 20,367, which is a profit/loss of 853 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Rune bar  3  Common  8,325 
Possibility 8  Gems
The expected value of Possibility 8 is 30,312, which is a profit/loss of 9,092 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Uncut diamond  3  Common  13,353  
Uncut ruby  3  Common  4,917 
Possibility 9  Loop half of a key
The expected value of Possibility 9 is 37,182, which is a profit/loss of 15,962 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Loop half of a key  1  Common  10,140  
Coins  15,000  Common  15,000 
Possibility 10  Tooth half of a key
The expected value of Possibility 10 is 38,401, which is a profit/loss of 17,181 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Tooth half of a key  1  Common  11,359  
Coins  15,000  Common  15,000 
Possibility 11  Rune platebody
The expected value of Possibility 11 is 49,522, which is a profit/loss of 28,302 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Rune platebody  1  Common  37,480 
Possibility 12  Rune platelegs or plateskirt
The expected value of Possibility 12 is 49,044 for male characters and 49,103 for female characters, which is a profit/loss of 27,824 for male characters and 27,883 for female characters, if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Rune platelegs  1  Common^{[1]}  37,002  
Rune plateskirt  1  Common^{[1]}  37,061 
 ^ ^{a} ^{b} With Possibility 12, you are guaranteed to get either a rune platelegs or rune plateskirt. Male characters will always receive a rune platelegs, while female characters will always receive a rune plateskirt.
Possibility 13  Dragonstone armour
The expected value of Possibility 13 is 7,466,314, which is a profit/loss of 7,445,094 if buying the crystal key on the GE.
 Receiving this possibility is very rare, at a rate of 1/6801.^{[1]}
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Dragonstone helm  1  Very rare^{[2]}  7,684,477  
Dragonstone hauberk  1  Very rare^{[2]}  13,270,490  
Dragonstone greaves  1  Very rare^{[2]}  6,133,880  
Dragonstone gauntlets  1  Very rare^{[2]}  5,932,094  
Dragonstone boots  1  Very rare^{[2]}  4,250,417 
 ^ https://twitter.com/JagexTimbo/status/557600452150579200
 ^ ^{a} ^{b} ^{c} ^{d} ^{e} With Possibility 13, you are guaranteed to get exactly one piece of dragonstone armour. Each piece has the same probability of being received.
Prifddinas chest
This chest was released with the first part of Prifddinas on 22 September 2014, and is located in the Iorwerth Manor against the south wall. It has an improved drop table over the chest in Taverley. At the least, the player should still wear a Ring of wealth when opening either crystal chest.
Possibility 1  Tree seeds
The expected value of Possibility 1 is 63,232.8, which is a profit/loss of 42,012.8 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Yew seed  1  Common  20,646  
Papaya tree seed  1  Common  3,742  
Elder seed  1  Uncommon  207,178 
Possibility 2  Herb seeds
The expected value of Possibility 2 is 14,283, which is a profit/loss of 6,937 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Dwarf weed seed  1  Common  1,007  
Torstol seed  2  Common  1,234 
Possibility 3
The expected value of Possibility 3 is 48,427, which is a profit/loss of 27,207 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Grimy lantadyme  5  Common  36,385  
Crystal tree blossom  1  Common  Not sold 
Possibility 4  Talismans
The expected value of Possibility 4 is 18,940, which is a profit/loss of 2,280 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Fire talisman  5 (noted)  Common  1,710  
Water talisman  2 (noted)  Common  5,188 
Possibility 5  Rune Halberd
The expected value of Possibility 5 is 21,784, which is a profit/loss of 564 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Rune halberd  1  Common  9,742 
Possibility 6  Ores
The expected value of Possibility 6 is 22,392, which is a profit/loss of 1,172 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Coal  80 (noted)  Common  8,160  
Adamantite ore  10 (noted)  Common  2,190  
Corrupted ore  50  Common  Not sold 
Possibility 7  Rune bars
The expected value of Possibility 7 is 20,367, which is a profit/loss of 853 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Rune bar  3  Common  8,325 
Possibility 8  Uncut gems
The expected value of Possibility 8 is 30,312, which is a profit/loss of 9,092 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Uncut diamond  3  Common  13,353  
Uncut ruby  3  Common  4,917 
Possibility 9  Loop half of a key
The expected value of Possibility 9 is 22,182, which is a profit/loss of 962 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Loop half of a key  1  Common  10,140  
Crystal motherlode shard  10  Common  Not sold 
Possibility 10  Tooth half of a key
The expected value of Possibility 10 is 23,401, which is a profit/loss of 2,181 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Tooth half of a key  1  Common  11,359  
Crystal motherlode shard  10  Common  Not sold 
Possibility 11  Rune armour
The expected value of Possibility 11 is 63,584, which is a profit/loss of 42,364 if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Rune full helm  1  Common  20,892  
Rune kiteshield  1  Common  30,650 
Possibility 12  Rune platelegs or plateskirt
The expected value of Possibility 12 is 49,044 for male characters and 49,103 for female characters, which is a profit/loss of 27,824 for male characters and 27,883 for female characters, if buying the crystal key on the GE.
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Rune platelegs  1  Common^{[1]}  37,002  
Rune plateskirt  1  Common^{[1]}  37,061 
 ^ ^{a} ^{b} With Possibility 12, you are guaranteed to get either a rune platelegs or rune plateskirt. Male characters will always receive a rune platelegs, while female characters will always receive a rune plateskirt.
Possibility 13  Dragonstone armour
The expected value of Possibility 13 is 7,466,314, which is a profit/loss of 7,445,094 if buying the crystal key on the GE.
 Receiving this possibility is very rare, at a rate of 1/6801.^{[1]}
Item  Quantity  Rarity  GE price  

Uncut dragonstone  1  Always  12,042  
Dragonstone helm  1  Very rare^{[2]}  7,684,477  
Dragonstone hauberk  1  Very rare^{[2]}  13,270,490  
Dragonstone greaves  1  Very rare^{[2]}  6,133,880  
Dragonstone gauntlets  1  Very rare^{[2]}  5,932,094  
Dragonstone boots  1  Very rare^{[2]}  4,250,417 
 ^ https://twitter.com/JagexTimbo/status/557600452150579200
 ^ ^{a} ^{b} ^{c} ^{d} ^{e} With Possibility 13, you are guaranteed to get exactly one piece of dragonstone armour. Each piece has the same probability of being received.
Probabilities
Taverley chest
 The probabilities in this section are an estimation based on the data of 1000 crystal chest loots on the Taverley chest, while wearing a luck of the dwarves.
Possibility  Percentage 

Possibility 1: Fruit tree seed  6.4%^{[notes 1]} 
Possibility 2: Lantadyme seeds  7.9% 
Possibility 3: Grimy torstols  9.4% 
Possibility 4: Runes  10% 
Possibility 5: Iron ore  9.1% 
Possibility 6: Coal  9.8% 
Possibility 7: Rune bars  9.4% 
Possibility 8: Gems  8.3% 
Possibility 9: Loop half of a key  7.4% 
Possibility 10: Tooth half of a key  6.8% 
Possibility 11: Rune platebody  7.2% 
Possibility 12: Rune platelegs or plateskirt  8.3% 
Possibility 13: Dragonstone armour  < 0.01% 
 ^ The official RuneScape wiki lists the probability of receiving a calquat or papaya tree seed at 5:11 (45.45%) each and the probability of receiving a palm tree seed at 1:11 (9%). This data shows a probability of 48.45% for the calquat, 42.18% for the papaya, and 9.37% for the palm tree seed.
Using these probabilities, the expected average profit/loss, per crystal key, when looting the crystal chest is 33,117. Assuming you will receive whichever of the rune platelegs and rune plateskirt is worth more, and the crystal key is bought at GE price. This is excluding the possibility of receiving a dragonstone armour piece, as this possibility is much too rare to estimate with any acceptable accuracy.
Prifddinas chest
 The probabilities in this section are an estimation based on the data of 20,000 loots of the Prifddinas crystal chest while wearing luck of the dwarves. The loot from the Prifddinas chest is not affected by the Voice of Seren.^{[1]}
Possibility  Percentage 

Possibility 1: Tree seeds  7.59% 
Possibility 2: Herb seeds  7.555% 
Possibility 3: Grimy lantadymes  4.47% 
Possibility 4: Talismans  7.545% 
Possibility 5: Rune Halberd  6.00% 
Possibility 6: Ores  10.36% 
Possibility 7: Rune bars  9.455% 
Possibility 8: Gems  9.525% 
Possibility 9: Loop half of a key  9.30% 
Possibility 10: Tooth half of a key  9.045% 
Possibility 11: Rune full helm and rune kiteshield  8.81% 
Possibility 12: Rune platelegs or plateskirt  10.34% 
Possibility 13: Dragonstone armour  < 0.01% 
Using these probabilities, the expected average profit/loss, per crystal key, when looting the crystal chest is 11,550. Assuming you will receive rune platelegs, the crystal key is bought at GE price and the luck of the dwarves ring is worn. This is excluding the possibility of receiving a dragonstone armour piece, as this possibility is much too rare to estimate with any acceptable accuracy.
Estimate probabilities for nonguaranteed loot are:
 17.785% chance of crystal motherlode shard when rolling possibility 9 or 10. This assumes that possibility 9 and 10 yield the same chance for crystal motherlode shards.
 8.675% chance of receiving elder seed when rolling possibility 1.
 63.385% chance of receiving papaya tree seed when rolling possibility 1.
 27.94% chance of receiving yew seed when rolling possibility 1.
 20.39% chance of receiving dwarf weed seed when rolling possibility 2.
 79.61% chance of receiving torstol seed when rolling possibility 2.
Trivia
 The crystal key chest was reworked on 11 June 2013 with the release of the Triskelion Treasures. Previous old drops, such as receiving 2,000 coins and a Spinach roll along with an Uncut dragonstone, were removed, and new ones were added, such as the Dragonstone armour.
 The estimated dragonstone armour possibility chance is about 0.000147%.
References
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