Hello.
Custom chests drop mechanics are one of the most critical systems we monitor closely. All drop chances strictly match the values specified in the database.
To verify correctness, we run synthetic drop simulations internally, performing 10 000 iterations per test. These simulations use the exact same RNG function as the live drop system, so there is no room for discrepancies or errors.
Drop chances are not a guarantee. They represent a statistical average over a large number of attempts. Someone could open their very first chest and receive a legendary weapon, or go hundreds of attempts without one. That is the nature of random chance.
To calculate the expected number of drops, use this simple formula:
attempts × (chance / 100) = expected drops
Here is an example from our first test using a standard legendary key:
12:39:31 --- START CHEST TEST
12:39:31 2 - [Warglaive of Azzinoth] entry: 32837, itemlevel: 156
12:39:31 51 - [Berserker's Call] entry: 33831, itemlevel: 133
12:39:31 54 - [Tsunami Talisman] entry: 30627, itemlevel: 128
12:39:31 59 - [Dragonspine Trophy] entry: 28830, itemlevel: 125
12:39:31 74 - [Blackened Naaru Sliver] entry: 34427, itemlevel: 154
12:39:31 78 - [Band of Ruinous Delight] entry: 34189, itemlevel: 154
12:39:31 78 - [Cloak of Unforgivable Sin] entry: 34241, itemlevel: 164
12:39:31 83 - [Shoulderpads of Vehemence] entry: 34195, itemlevel: 159
12:39:31 83 - [Gloves of Immortal Dusk] entry: 34370, itemlevel: 159
12:39:31 85 - [Dragonscale-Encrusted Longblade] entry: 34164, itemlevel: 154
12:39:31 85 - [Hard Khorium Choker] entry: 34358, itemlevel: 159
12:39:31 86 - [Shadowed Gauntlets of Paroxysm] entry: 34234, itemlevel: 159
12:39:31 87 - [Clutch of Demise] entry: 34177, itemlevel: 154
12:39:31 88 - [Hard Khorium Band] entry: 34361, itemlevel: 159
12:39:31 89 - [Shiv of Exsanguination] entry: 34197, itemlevel: 154
12:39:31 90 - [Duplicitous Guise] entry: 34244, itemlevel: 164
12:39:31 90 - [Carapace of Sun and Shadow] entry: 34369, itemlevel: 159
12:39:31 91 - [Hand of the Deceiver] entry: 34331, itemlevel: 164
12:39:31 91 - [Blade of Life's Inevitability] entry: 34349, itemlevel: 154
12:39:31 93 - [Bladed Chaos Tunic] entry: 34397, itemlevel: 159
12:39:31 94 - [Grip of Mannoroth] entry: 34203, itemlevel: 154
12:39:31 94 - [Muramasa] entry: 34214, itemlevel: 154
12:39:31 95 - [Fang of Kalecgos] entry: 34165, itemlevel: 154
12:39:31 96 - [Leggings of the Immortal Night] entry: 34188, itemlevel: 159
12:39:31 98 - [Golden Bow of Quel'Thalas] entry: 34196, itemlevel: 154
12:39:31 99 - [Crux of the Apocalypse] entry: 34329, itemlevel: 164
12:39:31 169 - [Bristleblitz Striker] entry: 30906, itemlevel: 151
12:39:31 170 - [Choker of Serrated Blades] entry: 32591, itemlevel: 141
12:39:31 171 - [Slayer's Belt] entry: 34558, itemlevel: 154
12:39:31 173 - [Mantle of Darkness] entry: 32377, itemlevel: 141
12:39:31 177 - [Shadowmaster's Boots] entry: 32366, itemlevel: 141
12:39:31 179 - [Shady Dealer's Pantaloons] entry: 30898, itemlevel: 141
12:39:31 180 - [Tracker's Blade] entry: 30865, itemlevel: 141
12:39:31 181 - [Midnight Chestguard] entry: 30905, itemlevel: 151
12:39:31 182 - [Deadly Cuffs] entry: 30863, itemlevel: 141
12:39:31 182 - [Shadowmoon Destroyer's Drape] entry: 32323, itemlevel: 141
12:39:31 183 - [Insidious Bands] entry: 32324, itemlevel: 141
12:39:31 184 - [Slayer's Shoulderpads] entry: 31030, itemlevel: 146
12:39:31 184 - [Choker of Endless Nightmares] entry: 32260, itemlevel: 141
12:39:31 186 - [Slayer's Legguards] entry: 31029, itemlevel: 146
12:39:31 188 - [Stormrage Signet Ring] entry: 32497, itemlevel: 151
12:39:31 188 - [Band of Devastation] entry: 32526, itemlevel: 151
12:39:31 189 - [Blade of Infamy] entry: 30881, itemlevel: 141
12:39:31 189 - [Slayer's Helm] entry: 31027, itemlevel: 146
12:39:31 189 - [Grips of Damnation] entry: 32347, itemlevel: 141
12:39:31 190 - [Syphon of the Nathrezim] entry: 32262, itemlevel: 141
12:39:31 191 - [Slayer's Chestguard] entry: 31028, itemlevel: 146
12:39:31 192 - [Razorfury Mantle] entry: 30917, itemlevel: 141
12:39:31 192 - [Sin'dorei Pendant of Triumph] entry: 35292, itemlevel: 141
12:39:31 194 - [Cursed Vision of Sargeras] entry: 32235, itemlevel: 151
12:39:31 196 - [Shadow-walker's Cord] entry: 32265, itemlevel: 141
12:39:31 196 - [Twisted Blades of Zarak] entry: 32326, itemlevel: 141
12:39:31 197 - [Boundless Agony] entry: 30901, itemlevel: 141
12:39:31 199 - [Slayer's Boots] entry: 34575, itemlevel: 154
12:39:31 201 - [Don Alejandro's Money Belt] entry: 30879, itemlevel: 141
12:39:31 202 - [Swiftsteel Bludgeon] entry: 32943, itemlevel: 141
12:39:31 203 - [Black Bow of the Betrayer] entry: 32336, itemlevel: 151
12:39:31 205 - [Black Featherlight Boots] entry: 30891, itemlevel: 141
12:39:31 205 - [Nether Shadow Tunic] entry: 32252, itemlevel: 141
12:39:31 207 - [Shard of Azzinoth] entry: 32471, itemlevel: 151
12:39:31 207 - [Slayer's Bracers] entry: 34448, itemlevel: 154
12:39:31 208 - [Messenger of Fate] entry: 32269, itemlevel: 141
12:39:31 209 - [Sin'dorei Band of Triumph] entry: 35284, itemlevel: 141
12:39:31 210 - [Slayer's Handguards] entry: 31026, itemlevel: 146
12:39:31 210 - [Blade of Savagery] entry: 32369, itemlevel: 141
12:39:31 213 - [Ring of Deceitful Intent] entry: 32266, itemlevel: 141
12:39:31 216 - [Madness of the Betrayer] entry: 32505, itemlevel: 141
Only 2 Warglaives dropped, which lines up with the expected average given the 0.014% drop chance:
10000 × (0.014 / 100) = 1.4 expected drops
The Flawless Legendary Key multiplies the legendary drop chance by 30x. Here is the same test using one:
12:37:46 --- START CHEST TEST
12:37:50 48 - [Warglaive of Azzinoth] entry: 32837, itemlevel: 156
12:37:50 49 - [Tsunami Talisman] entry: 30627, itemlevel: 128
12:37:50 56 - [Dragonspine Trophy] entry: 28830, itemlevel: 125
12:37:50 56 - [Berserker's Call] entry: 33831, itemlevel: 133
12:37:50 71 - [Duplicitous Guise] entry: 34244, itemlevel: 164
12:37:50 71 - [Crux of the Apocalypse] entry: 34329, itemlevel: 164
12:37:50 74 - [Fang of Kalecgos] entry: 34165, itemlevel: 154
12:37:50 79 - [Leggings of the Immortal Night] entry: 34188, itemlevel: 159
12:37:50 81 - [Band of Ruinous Delight] entry: 34189, itemlevel: 154
12:37:50 81 - [Blackened Naaru Sliver] entry: 34427, itemlevel: 154
12:37:50 82 - [Cloak of Unforgivable Sin] entry: 34241, itemlevel: 164
12:37:50 83 - [Grip of Mannoroth] entry: 34203, itemlevel: 154
12:37:50 85 - [Muramasa] entry: 34214, itemlevel: 154
12:37:50 87 - [Shoulderpads of Vehemence] entry: 34195, itemlevel: 159
12:37:50 90 - [Hand of the Deceiver] entry: 34331, itemlevel: 164
12:37:50 90 - [Carapace of Sun and Shadow] entry: 34369, itemlevel: 159
12:37:50 91 - [Dragonscale-Encrusted Longblade] entry: 34164, itemlevel: 154
12:37:50 92 - [Hard Khorium Choker] entry: 34358, itemlevel: 159
12:37:50 93 - [Bladed Chaos Tunic] entry: 34397, itemlevel: 159
12:37:50 94 - [Hard Khorium Band] entry: 34361, itemlevel: 159
12:37:50 95 - [Blade of Life's Inevitability] entry: 34349, itemlevel: 154
12:37:50 95 - [Gloves of Immortal Dusk] entry: 34370, itemlevel: 159
12:37:50 101 - [Shadowed Gauntlets of Paroxysm] entry: 34234, itemlevel: 159
12:37:50 102 - [Shiv of Exsanguination] entry: 34197, itemlevel: 154
12:37:50 106 - [Clutch of Demise] entry: 34177, itemlevel: 154
12:37:50 106 - [Golden Bow of Quel'Thalas] entry: 34196, itemlevel: 154
12:37:50 175 - [Cursed Vision of Sargeras] entry: 32235, itemlevel: 151
12:37:50 176 - [Slayer's Shoulderpads] entry: 31030, itemlevel: 146
12:37:50 178 - [Slayer's Legguards] entry: 31029, itemlevel: 146
12:37:50 180 - [Sin'dorei Pendant of Triumph] entry: 35292, itemlevel: 141
12:37:50 181 - [Deadly Cuffs] entry: 30863, itemlevel: 141
12:37:50 181 - [Shady Dealer's Pantaloons] entry: 30898, itemlevel: 141
12:37:50 181 - [Slayer's Helm] entry: 31027, itemlevel: 146
12:37:50 181 - [Nether Shadow Tunic] entry: 32252, itemlevel: 141
12:37:50 181 - [Ring of Deceitful Intent] entry: 32266, itemlevel: 141
12:37:50 183 - [Black Featherlight Boots] entry: 30891, itemlevel: 141
12:37:50 184 - [Messenger of Fate] entry: 32269, itemlevel: 141
12:37:50 184 - [Grips of Damnation] entry: 32347, itemlevel: 141
12:37:50 184 - [Stormrage Signet Ring] entry: 32497, itemlevel: 151
12:37:50 185 - [Choker of Endless Nightmares] entry: 32260, itemlevel: 141
12:37:50 187 - [Black Bow of the Betrayer] entry: 32336, itemlevel: 151
12:37:50 187 - [Shard of Azzinoth] entry: 32471, itemlevel: 151
12:37:50 188 - [Slayer's Boots] entry: 34575, itemlevel: 154
12:37:50 189 - [Shadow-walker's Cord] entry: 32265, itemlevel: 141
12:37:50 189 - [Shadowmoon Destroyer's Drape] entry: 32323, itemlevel: 141
12:37:50 190 - [Razorfury Mantle] entry: 30917, itemlevel: 141
12:37:50 190 - [Syphon of the Nathrezim] entry: 32262, itemlevel: 141
12:37:50 190 - [Twisted Blades of Zarak] entry: 32326, itemlevel: 141
12:37:50 190 - [Slayer's Belt] entry: 34558, itemlevel: 154
12:37:50 191 - [Madness of the Betrayer] entry: 32505, itemlevel: 141
12:37:50 192 - [Don Alejandro's Money Belt] entry: 30879, itemlevel: 141
12:37:50 194 - [Slayer's Chestguard] entry: 31028, itemlevel: 146
12:37:50 195 - [Tracker's Blade] entry: 30865, itemlevel: 141
12:37:50 195 - [Swiftsteel Bludgeon] entry: 32943, itemlevel: 141
12:37:50 196 - [Midnight Chestguard] entry: 30905, itemlevel: 151
12:37:50 196 - [Shadowmaster's Boots] entry: 32366, itemlevel: 141
12:37:50 197 - [Boundless Agony] entry: 30901, itemlevel: 141
12:37:50 197 - [Slayer's Handguards] entry: 31026, itemlevel: 146
12:37:50 198 - [Slayer's Bracers] entry: 34448, itemlevel: 154
12:37:50 199 - [Sin'dorei Band of Triumph] entry: 35284, itemlevel: 141
12:37:50 201 - [Choker of Serrated Blades] entry: 32591, itemlevel: 141
12:37:50 202 - [Bristleblitz Striker] entry: 30906, itemlevel: 151
12:37:50 203 - [Blade of Savagery] entry: 32369, itemlevel: 141
12:37:50 204 - [Band of Devastation] entry: 32526, itemlevel: 151
12:37:50 206 - [Insidious Bands] entry: 32324, itemlevel: 141
12:37:50 216 - [Mantle of Darkness] entry: 32377, itemlevel: 141
12:37:50 226 - [Blade of Infamy] entry: 30881, itemlevel: 141
This time 48 Warglaives dropped, slightly above the mathematical average. That is perfectly normal due to random variance:
10000 × (0.014 × 30 / 100) = 42 expected drops
Regarding Bladed Chaos Tunic - as you can see from the logs, this item drops correctly.
If you have any further questions about how the drop system works, feel free to ask.