TL;DR around 0.3% to 0.5% I got bored and wanted to take a break from working an Idol/ Raid guide... so I decided to go through all my data for Epic Quests, for the past 412 days I have made note of every single epic quest I have had (hopefully I did not miss any edit: I did miss 3-4 months of data, this is address below). The results from this can be seen in the table below At a glance I have had 38 total Epic Adventures in the past 412 days. OBSERVATION A: In order to calculate the probability I needed to make some guesstimations for the total number of adventures I have seen over the same period. See this estimation below, So there is about a 0.307% chance of getting an epic quest based purely on the above. However, I would guess the true probability to be more like 0.3-0.5% because I missed 3-4 months of data collects. In late 2017 to early 2018 I did not record any epic quests, likely because I forgot to screenshot them Also, 0.5% seems like a nice and easy number. OBSERVATION B: Over the life of the game ATA has periodically introduced new adventure titles. The quests in table 1 are ordered in chronological order of when they first appeared (to me). See the graph below to more visually see this, The left of the data, this suggests that there have been more of the "older adventure names". This makes sense because they have been around longer. Also Slay Ib the Nibbler and Slay Zubbix the Flatulent were seen for the first time within the the past month or two.