Essence

Q: How do I get essence?

You get essence by clearing a new wave in a run/prestige, meaning that if you die and have to repeat some waves, you won't get essence for waves you've beaten already. But keep this in mind: prestiging clears your run's highest wave, meaning you can start obtaining essence again from wave 1. You can also get essence by using the Essence Storm spell, destroying Cargo Ships, collecting Daily Rewards, opening Resource Packs, and, if you have the right upgrades, you can also get essence from Haulers and non-spawned Boss ships (the ones that spawn every -5 and -0 waves).

Q: How do I get more essence?

If you don't have Boss Essence Drop upgrades, playing normally and prestiging often is the best way to gain essence. However, when you do get at least one level in the upgrade mentioned before, it might be better to start using the Boss Rush option, as every wave you'll start getting an enemy that drops essence, along with getting the same as if you were progressing without Boss Rush. There are plenty of ways to increase essence gain (All types of upgrades except Premium and Gem Upgrades, if you exclude Resource Packs).

Q: Where do I use/spend my essence?

You can use your essence to open decks, unlock new monsters or improve the ones you have. You can also spend your essence to level up your Spells and your Research upgrades, spawn Tech Ships, and upgrade Exotic Skills. Note that when improving monsters you have (increasing your Multi-Card DPS), it's usually considered a short-term form of progression if it's not on a Godly monster, as you should end up replacing your current monsters with Godly Tiered ones when they become available to you.