If you want to progress in Battlejack, it is extremely important to keep levelling up your Heroes. You will most definitely need those improved stats if you are to beat Chaos.

Upgrade a hero in your hero collection by opening the hero card. Tap Upgrade and select a hero to fuse into the hero you are upgrading. The heroes you fuse are sacrificed and disappear from your hero collection, so don't sacrifice all of them.Be clever about it - don't fuse a Legendary Hero Card into a Blop unless you're really sure! (Hint: This is never a clever idea)The other way around, however? Go for it!

Each Hero Card has a maximum level you can achieve before you can Evolve it further. An Elder Fire Troll might have a maximum level of 10. Once you have Fused enough Cards into your Elder Fire Troll, you can Evolve itto the next level.

Upgrading also costs some gold. If you run out of gold you can get more by opening chests or selling heroes from your hero collection.

There are special ghost heroes that give a lot more XP when fused into another hero. They will level up your other heroes in no time. There is a special event for capturing those ghosts once per week.

You can also join a guild and ask your fellow guild members to help level up your heroes. Make a Fuse Request, and your guild mates can donate sacrifices to level up your hero. Remember to return the favor by donating heroes to your guild mates.