Souls are coins used to upgrade your heroes mercenaries and you get so many every hour depending on your rank on the leaderboard. Souls are also required for evolving heroes at certain levels. You can get them from leaderboard rankings and guild rankings if your guild is in the top 50, dungeons, achievements, and with mugs.
Ways of getting souls
1. Lords League, you will get souls every hour, and how much souls you get depends on your ranking in the league.
By raiding a base in Lords League, not only you will get trophies, you will get some souls as well.
2. Dungeons, it rewards you a certain amount of souls the first time you got a 3 stars from the stage. Subsequently, the chest you get from dungeons rewards you with souls as well.
3. Quest, certain quest's rewards come with souls. E.g. By completing The Lord's path quest (Win 1500 Glory Trophies) gives you 60 rings and 1000 souls.
4. Dancing Dragons, a reward gamble where you can exchange mugs for 500-2500 souls per mug. You can also exchange jewels for 500-10k souls. Each time you exchange gems for souls the jewel cost increases.
5. Continent Ranking, Get season rewards by rank in your continent. The higher your rank, the higher the rewards. Gain glory trophies in lord's league (and lord's defense) in order to increase your rank.