Phobos

Phobos is a very hard demon level created by Tygrysek and other more creators. The level was considered as one of the hardest levels in Geometry Dash, however it was downgraded due to hacks, the original level however was near-impossible and was later nerfed.

As of May 12, 2016, Krazyman50 has verified the level legitimately. The level has since been reuploaded under his account where it regained its own demon rating.

Gameplay
KoBaZz - Confusing but simple mini cube part which requires crucial timing, filled with fake jump rings and gravity portals.

Honeyb - The background and ground turns dark, and will enter a wave mode, which is moderately hard, Acropolis-like and requires crucial timing. The coloured spikes in the Honeyb part will slightly change into black and white, then the cube mode which will last for a second will come and changes into a hard mini wave mode. The seemingly obvious route is blocked by a sawblade and requires to go under, then you will see Honeyb's name.

TechneT - Another cube part similar to those of KoBaZz's follows up but is slightly harder and needs more crucial timing. The design of his part is similar to those of Steam Chamber by Darnoc. It also resembles his own demon rated level, called Mechanic Megaforce.

GMTSean - A very confusing UFO and requires very precise timing and jumps.

Jobet - A slow ship part with somewhat tight spaces. The ship has gravity changes, a couple of mirror portals, speed changes, and gravity portals that easily confuse inexperienced players. After this, Jobet's name will be seen.

Eduard0 - A wave that is extremely difficult due to tight spaces, sawblades and double speed.

iBlade - The player transitions to a mini ball. This part is tricky and requires more timing and jumps, especially switching gravity at the very end of platforms to avoid a spike on the other side. This is followed by a very tight wave with gravity portals. iBlade's name moves up letter by letter at the start of this wave, suggesting it was added during 2.0, iBlade's part closely resembles WOOGI's part in The Ultimate Phase.

Palery - A mini ship with many speed changes, designed to throw the player off. A triple speed mini wave with invisible slopes follows, but is rather simple in comparison to some parts of the level. (Originally, the first double-speed portal has a pink jump ring spike jump which is ridiculously hard)

TerraSmokes - The level's color suddenly changes into green. The player turns into a mini ball. This part has an annoying amount of precise timing, and most of the level composes of fake lining and invisible platforms. Then comes a UFO with purple background.

Jo2000 - Considered to be one of the hardest parts. It starts with a half speed ship with jump rings, gravity portals and extremely tight spaces. Halfway through, the player goes mini and completes the ship. (As seen in the picture above)

DreamEater - a hard triple speed wave with a gravity switch halfway, then another straight fly segment with size changes and gravity portals everywhere. There is a brief wave section towards the end.

Tygrysek - a triple speed dual ship which briefly becomes half speed in the middle.

Iqrar99 - A really hard mixed dual of UFO and Ball mode, similar to Ditched Machine.

Skitten - A normal speed ship with clusters of sawblades. The part has many gravity portals and yellow jump rings that are hard to time. The player suddenly changes to a UFO with many gravity portals and more jump rings.

Kubs0n - In the old version, this part starts off with a mini ship, than changes to a mini wave leading through tight spaces, difficult timings and hard to notice objects. Mini wave gameplay is slightly similar to a part from Sonic Wave. In the nerfed version, rather than being in the mini-wave, you are a regular wave.

Andromeda - It resembles the looks of Andromeda's collab Lunatic Doom Machine, that is filled with crosses, with an upside down half speed ship with a 1 block straight fly.

Caernarvon725 - Made after the release of 2.0, this ball mode has many tight spaces, speed and size changes and crucial timing. "Caernarvon" can be seen towards the end.

Razur - His name appears, then you will be teleported up to a short, but hard UFO part with moving obstacles requiring somewhat difficult timings.

WOOGI - The gamemode will become a ship, then a short ball mode, then a ship again. A rotating group of sawblades, being rotated by a Mode trigger which needs to be dodged, if not, can be hit. This part requires a notorious amount of straight fly and is quite difficult. A robot part will seen but last for a second, then back to a triple speed cube. A "Take a Break" text will appear.

Riqirez - The last part is a ship, with a cluster of small invisible spikes and blocks, portals, jump pads, and jump rings can be seen, resembling NePtunE's demon Doomsday II (albeit in ship mode). There are crosses made out of glow can be seen.

The level will end as a hall of the people who participated in the megacollab, with the sentence: "Congratulations! You have completed one of the hardest megacollabs in GD!". Underneath is 'Hacked by Tygrysek' then is replaced by 'Verified by Krazy" (originally "Verified by Tygrysek").

Crashes/Fails

 * Krazyman50 crashed at 73% twice, 78%, 81%, 82%, 84% and 87%.
 * Surv crashed at 87% twice.

Trivia

 * Phobos is considered to be one of the hardest levels ever to be created in Geometry Dash, because the level is extremely long and has annoying amounts of difficult timing and straight-fly. Some consider it to be on par with or even harder than Bloodbath.
 * To date Surv and Krazyman50 are the only players to beat the level legitimatety.
 * COSINE and DryBones were originally planned to be in the collaboration, but they never replied to requests.
 * Riqirez's part was originally a near-impossible part (it used to be a mixed dual mini ship and cube), until Tygrysek reverified the level and nerfed it into a mini ship mode.
 * The original level was threatened to be unrated due to the fact that Tygrysek hacked it, so then he changed it into a free demon. It was then changed it back to its original version and then the level was unrated due to hacks by someone tipping off RobTop and then removed from the servers.However is reuploaded by Krazyman50.
 * EndLevel may've completed Phobos off camera and has video evidence but it may be hacked.
 * GMTSean, one of the creators of Phobos, has also uploaded the unnerfed version of Phobos (there is a secret way at the end of Kobazz's part to allow Sean to easily verify the level).