Champion Merits are primarily used to uncap characters. They are needed for the later stars on SR and SSR characters.
|Uncap story SR to 3★||3|
|Uncap story SR to 4★||3|
|Uncap SR to 4★||3|
|Uncap SR to 5★||3|
|Uncap SSR to 5★||6|
|Rebuild Class Champion Weapons||30|
|Awaken Revenant Weapons||50|
|Purchase Legendary Merit from the shop||10|
The most common way to get Champion Merits is from Proto Bahamut. They are a fairly common drop, and most players will run it many times for Horn of Bahamut and Rusted Weapons. The only caveat is that you must be rank 50 to see Proto Bahamut raids, and they tend to only show up in the raid list rarely and fill up quickly. For players not yet rank 50, many events have Champion Merits as a reward in some format. For Showdown events, they are available in the event shop. For Story events, they are usually in the honor collection rewards.