Foundables are artefacts, beasts, people and even memories of the wizarding world appearing in present-day Muggle reality. Examples of Foundables include, but are not limited to:
- Hypogriff: You must break the ball-chain shackling the beast
- Dementor: Use a Patronus spell to get rid of it
- Demiguise: Free it from its chains using a Alohomora spell
- Professor: Free the Professor from the bottle
For a complete list of all potential Encounters, click here.
Collecting a specific number of Fragments for a specific Foundable will reward you an AR sticker and points in the category the Foundable goes to, which will increase your abilities for that given category.
Going beyond the required amount to unlock an AR sticker will allow you to start over into Prestige mode, which reportedly is the same sticker but with an increased difficulty in order to complete it. Perhaps this will be a way for Niantic to include variants of these stickers.
Early reports indicate that exiting a Trace/Foundable will result in it no longer being accessible afterwards.
Infographic from Orange Wizard 2019