In Last Epoch it is possible to change your Skill Points, Passive Points, Blessing and Mastery Choice. Some of these require the help of a Chronomancer, these NPCs are indicated on the map by a purple brain icon for Chronomancer Lerinne and a gold brain icon for Chronomancer Nyx.
Passive Points can be respecialized with Chronomancer Lerinne in Towns. This is also who can help you respecialize your Mastery, however this can only be done in the End of Time.
You can also swap your equipped Blessings with Chronomancer Nyx in the End of Time near the Monolith of Fate gates.
Skills and skill points can be respecialized through the Skill window, however any points above the minimum skill level must be re-earned.