If you need to reset a Heroes Talent Grid, there is a reset button which can be activated using two methods.

Using a Reset Emblem - Using a Reset Emblem will return 100% of the Emblems used on the Talent Grid. Please be aware, only the Emblems spent on this Talent Grid will be returned, not the resources (Food and Iron). Reset Emblems can be obtained as loot from Wanted Missions, Titan Chests, Alliance Wars and Challenge Events.

Using Gems - Using Gems to reset a Talent Grid will return 95% of the Emblems used for the Talent Grid. Please be aware, only the Emblems spent on this Talent Grid will be returned, not the resources (Food and Iron).