Once you finally beat level 80, you will unlock the ability to get artifacts. An Artifact is purchased in exchange for relics, which can be acquired from reaching new levels and beating the bosses that come with them. Once you have an artifact, you can then level it up or purchase a new artifact when it becomes available in future levels.
The artifacts, of course, are completely random. If you spend diamonds, you can then break down the artifact for more relics if you don’t like it, and then you can use the relics to purchase another artifact.
If you want to unlock more special powers for your own hero, rather than for your ally fighters, then upgrade your taps and you’ll unlock them as soon as you hit specific levels. Tap on the picture on the left side of the tap upgrade area to see what the skills and levels are. The sixth one is the Midas Touch, which earns you coins with every tap. Use this as often as you can (it has a one dollar cooldown).
All of the other abilities work best for when you are fighting bosses, so save them and use all of them at once against a boss. Then as soon as you hit the next level, if you have the Midas Touch available, use it since the gold earned per tap will be higher depending on the level.
You can play the game offline without any WiFi or cellular data, but if you do this you won’t be able to watch all of the advertisement videos that pop up as offers for free diamonds, gold and other good stuff. Play the game online whenever possible.
Any time that you are in a boss battle without any of your power ups, if you want to wait for your power ups to come back without failing a boss battle, then all that you have to do is shut the game off for the time that it takes to get them back. You can also minimize the game and it will accomplish the same thing. Just wait for the time that it takes for the cooldowns to end, and when you come back to the boss fight you’ll have your skills back, and the boss timer won’t drop at all.