Use a total of 20 character(s) to form a team with Sampo and win at least 1 battle.
This achievement requires you to run Sampo with 20 unique characters, winning a fight alongside each one. If you put in 3 unique characters on each fight, the quickest you can achieve this is in 7 runs.
This requires you to either own Sampo, which allows you to borrow any missing characters using the summon system to hit the 20. Otherwise you will have to own 20 characters, allowing you to use your summon slot on Sampo.
The best location to farm these battles is on a level 1 echoes of war after you've exhausted your runs for the week. This lets you use summons without spending fuel as many times as you want.
