Well, I made an event which contains several elements. Paper chase! Somehow. Got inspired by SE's brutal riddle questline : )

The event starts in the FC House. Players are set in teams of 2, 3 or 4 (dependend on the size of the FC). Players have to find "NPCs" (FC volunteers or friends) who are spread all around the world. The location is rather unknown, but hints are placed near the house. Speaking with the NPC, players will get new riddles/hints or items. Sometimes they had to answer to a question or make a specific emote. At the end, players must find the last NPC, survive a fight using a specific potion or trade a set of right items to the start NPC.

Hints can be:
- Overpriced specific items on marketboard, where the price is a code
- Morse code, anagrams, alpha-numeric pattern in house-, room-descriptions
- Riddles from player NPCs
- weird ordered items in the guild storage
- retainers with items placed hidden in or outside the house
...

An example of my event 2 years ago:
1. Players must enter a specific players room. To unlock it, they must solve (saying) the morse code which is stated at the room description.
2. A NPC is waiting and stating, that something is watch trough the window. Players must leave the house to find a retainer behind the house.
3. This retainer got items like a framed picture of ul'dah landscape, alchemist gear and ul'dah dye. So they have to travel to the alchemist guild in ul'dah.
4. There, another NPC will give them a cloze with rhymes. It contains the location of the last NPC and what to do there. This NPC asks the player a question. The right answer give them a potion.
5. At the last location, another NPC is waiting. The first player/team who is using his potion in front of the NPC wins.