Flip Chests are gold chests typically from raid or event bosses that perform a little flip under a rainbow while playing a special sound.
Flip chests for SSR weapons/summons are notorious for having abysmal drop percentages (the most commonly cited number is 2%). However, depending on the boss being killed, they also usually guarantee a rare item of some sort.
Tier 1 Raids[]
The commonly farmed Omega raids have a possibility to drop 2 flip chests normally, with the vice MVP gold chest also given a chance to flip. The two normal flip chests are separate (in other words, there is an infinitesimal chance that you can get both of them at once), and the loot from one of the two chests is known to always be an Omega summon, while the other chest has one of the four Omega weapons associated with that boss. The vice MVP flip chest can be either a weapon or a summon.
Tier 2 Raids[]
There isn't as much data on the tier 2 raids yet, but what is known is that they do not drop Omega summons, but have added the tier 2 raid weapons to the pool. The assumption, then, is that there is only 1 possible flip chest that can contain any of the 6 weapons. There is another flip chest that drops Omega Animas.
| Twin Elements | Macula Marius |
|---|---|
 Colossus Cane Omega Colossus Carbine Omega Colossus Fist Omega Colossus Blade Omega Ecke Sachs Ancient Ecke Sachs Twin Elements Omega Anima |
 Leviathan Gaze Omega Leviathan Spear Omega Leviathan Scepter Omega Leviathan Bow Omega Auberon Ancient Auberon Macula Marius Omega Anima
|
| Medusa | Nezha |
 Yggdrasil Crystal Blade Omega Yggdrasil Dagger Omega Yggdrasil Dewbranch Omega Yggdrasil Bow Omega Perseus Ancient Perseus Medusa Omega Anima |
 Tiamat Gauntlet Omega Tiamat Glaive Omega Tiamat Amood Omega Tiamat Bolt Omega Nalakuvara Ancient Nalakuvara Nezha Omega Anima
|
| Apollo | Dark Angel Olivia |
 Luminiera Sword Omega Luminiera Bhuj Omega Luminiera Harp Omega Luminiera Bolt Omega Artemis Ancient Artemis Apollo Omega Anima |
 Celeste Claw Omega Celeste Horn Omega Celeste Zaghnal Omega Celeste Harp Omega Cortana Olden Cortana Dark Angel Olivia Omega Anima
|
Tier 3 Raids[]
Same as tier 2, there isn't as much data on the tier 3 raids yet, and they drop Omega weapons in addition to tier 3 raid weapons.
| Athena | Grani |
|---|---|
Colossus Cane Omega Colossus Carbine Omega Colossus Fist Omega Colossus Blade Omega Erichthonius Sword of Pallas |
Leviathan Gaze Omega Leviathan Spear Omega Leviathan Scepter Omega Leviathan Bow Omega Bow of Sigurd Wilhelm
|
| Baal | Garuda |
Yggdrasil Crystal Blade Omega Yggdrasil Dagger Omega Yggdrasil Dewbranch Omega Yggdrasil Bow Omega Solomon's Axe Spymur's Vision |
Tiamat Gauntlet Omega Tiamat Glaive Omega Tiamat Amood Omega Tiamat Bolt Omega Indra's Edge Plume of Suparna
|
| Odin | Lich |
Luminiera Sword Omega Luminiera Bhuj Omega Luminiera Harp Omega Luminiera Bolt Omega Gungnir Sleipnir Shoe |
Celeste Claw Omega Celeste Horn Omega Celeste Zaghnal Omega Celeste Harp Omega Obscuritas Phantasmas
|
Rank 80 Raids[]
Proto Bahamut and Grand Order switch things up a bit since they can drop rare crafting materials, which also come from a flip chest. 
Supreme Merits and 
Blue Sky Crystals, unlike previous flip chests, replace normal drops (usually 
Champion Merits) and eschew the 2% drop rate, while the 
Horn of Bahamut replaces the guaranteed Rusted Weapon drop but still has a very low drop rate.
| Proto Bahamut | Grand Order |
|---|---|
| Horn of Bahamut Supreme Merit Bahamut Weapons (0★) |
Twin Elements Omega Anima Macula Marius Omega Anima Medusa Omega Anima Nezha Omega Anima Apollo Omega Anima Dark Angel Olivia Omega Anima Supreme Merit Blue Sky Crystal
|
Impossible Raids[]
For the tier 1 raids, in addition to the same summons/weapons as the Extreme versions, they also have a 100% chance to drop matching-element Centrums, which always flip.
For the tier 2 raids, in addition to the same weapons as the Extreme versions, they also have a 100% chance to drop matching-element Urns, which always flip.
Showdowns and Collabs[]
Maniac and Nightmare bosses have a low chance to drop Urns corresponding to the boss's element in flip chests. In addition, Very Hard and above bosses can drop event 
weapons and/or summons from flip chests, with higher difficulties having higher chances. The rate of event flip chests is much much higher than 2%.