This part of the event only takes part on a map with a glowing sun with particles coming off of it (top left), fountain of blood (right), a giant pit (bottom). This map appears randomly in normal rooms.
This map contains a special mechanic: You can jump forward very far by pressing ↓ and then ↑ (while still pressing down).
To earn title, you must go into the "portal" at top left (the sun). To do this you must go to the top of the fountain, then jump on top of the outlines for the bottom of the leaves on the trees (to the left). once you reach the last tree and are on top of the left most outline squiggle, face towards then sun and press down and up.
You can also cross the pit to the "lava waterfall", but will only be given the message "Get back to your world".
Various things happened in this part to unlock the solo part above.
- Some normal maps starts showing a crack in the middle of the screen, and the map name would change to "Helloween"
- Doing certain things caused the crack to grow[confirm], and after growing enough would kill all the mice in the room.
- The following rooms appeared for event:
- #helloween0strongbox - The second living room was the salon # helloween0strongbox. It had a square containing 12 small squares.
- #helloween0hoover28 
- #helloween0uryybjrra and #helloween0arrjbyyru - The first room was found from the "Qvq lbh gel ebg kvvv ?" hint giving "Did you try rot xiii ?" when using a Caesar cipher of 13, meaning that you have to use a Caesar cipher of 13 (xiii) on "helloween" word. These map shows two counters going up to 25. If the map is viewed in /debug mode, "mirror" can be seen upside down, getting the name of the second map. It was then necessary to get 25 mice in both rooms to unlock next part.
- #helloween0temple - While active this map had platforms a health bar along the top, and the anvil god which mice had to defeat. Doing so set off some fireworks and showed the message "Something has changed in regular rooms !" . This unlocked the next portion of the enigma (see solo part above).
Crossing the giant pit on the blood fountain map during this phase would either earn you a hint, or if unlucky  would output a random ASCII picture of a mouse.
ASCII mouse art
_ _ (o)(o)––. \../ ( ) m\/m--m'`––.
(`–()_.–=–. /66 , , \ =(o_/=//_( /======` ~"` ~"~~`
_ .–.(c) (_____( ) , "–. `~ ~""`
- Enigma design by Podoko #0000.
- At one point one of the rooms had to be reset as someone who knew the event answer beforehand accidentally finished the room (for the community part).