To avoid any spoilers I will only list them based on their job as written in game, not by their name. Mostly I just write their in-game information too or just try to simplify them.
Obtained by default → Seneschal:
- Other followers level depend on her level.
- Craft random keys
Scroll Color (For upgrading to Epic and above): Yellow
End of Chapter 1 → Armorer:
- Craft random armors
End of Chapter 2 → Guard:
- Increase Gear, Spell, and Minion inventory space by 1 per level.
- Increase Chest inventory slots by 1 per rarity upgrade
Scroll Color (For upgrading to Epic and above): Blue
End of Chapter 3 → Farmer:
- Produces Food per hour
- Number of hours of Food can be stored increases per rarity upgrade
Scroll Color (For upgrading to Epic and above): Green
End of Chapter 4 → Miner:
- Produces Ore per hour
- Number of hours of Ore can be stored increases per rarity upgrade
End of Chapter 5 → Mystery:
- Increase Food capacity
- Increase Ore capacity
- Increase Gold capacity per rarity upgrade
End of Chapter 6 → Bard:
- Increases PvP stats (Power, Vitality, Masteries)
- Extra Tourney Token per day per rarity upgrade.
End of Chapter 7 → Artisan:
- Craft random accessories
End of Chapter 8 → Mage:
- Craft random spells
(An important follower IMO since you can get various spells from other classes too. I also still don’t know whether you can get all spells in the game by leveling 5 hero classes to 50 or you can only get certain spells from crafting & chests)
End of Chapter 9 → Weaponsmith:
- Craft random weapons
End of Chapter 10 → Locksmith:
- Craft Skirmish or Dungeon Loot Ticket
- There is small chance percentage of creating two tickets instead of one.
- Leveling up will increase the chance for Dungeon Loot Tickets
End of Chapter 11 → Runesmith
- Craft random shards (all kinds of shards: weapon, armor, accessory, spell, and minion shards)
End of Chapter 12 → Stable Master
- Craft random minion
End of Chapter 13 → Merchant
- Coin Bonus +0.5%
- Produces 100 Gold per hour
- Can store 1 hour of Gold
(Yeah it’s useless - I just write the stats since I believe I don’t plan to upgrade this one in a very long time)
End of Chapter 14 → Hunter
- Craft random Rune or Scroll
(Yup this one is very useful for evolving items and most importantly your followers)
Cost of Evolving Followers:
Common → Uncommon = 4 Uncommon Scrolls + 2000 Coins
Uncommon → Rare = 4 Rare Scrolls + 5000 Coins
Rare → Epic = 4 Specific Color Epic Scrolls + 10000 Coins
Hopefully this information helps.