This is an easy way to get talisman fragments, up to 1 a minute with high level rarity.
How to Farm Talisman Fragments
To start you need to have Field J2 beaten on journey mode. Open up the map and set all battle traits to max. start the map on endurance mode.
Once in the map put down towers around each of the chests. Put a grade 1 gem in just 1 tower next to each chest as seen below. set both gems targeting to structure, you can do this by right clicking and holding the gem and then move the mouse down. when you are ready call all waves by holding ctrl and clicking the wave stones.
When you get enough charge in the bolt strike spell put it on both of the gems. Once both chests are opened click on 1 of the stones to stop it from calling the rest of the waves and let yourself die. Rinse and repeat.