To combine a collection you need 5 collection items and the required number of fixers (items required to combine collections). Once a collection is complete, the Combine button in the Collections window will turn green.

Some collections can transform into artifacts that have the same characteristics as talismans.

You can get fixers as a reward for trading with townspeople and banishing or placating creatures. You can also get them as gifts from your friends (don't forget to update your Wish List!).

The most basic fixers can be obtained by successfully exploring locations and solving puzzles. High-level fixers can be crafted at merchants' shops.