Most players don't realize this, but Ash in Hades 2 is an important resource, as are Silver and Bronze Nodes. While the latter is used to brew Incantations at Concoct, Ashes work as a currency to obtain Arcana Cards. Since the game follows a typical method of collecting materials, you will have to do the same. For Ashes, we have created this guide that can help you find it and use it for your growth.
The most common method of obtaining Ash is through room rewards in various biomes, starting with Erebus. During your run you will come across places where you must choose a specific room to enter. The reward you get for clearing that room will appear on the door itself. So if you're specifically farming Ash in Hades 2, it's recommended that you enter a room that rewards you with it. Ash is represented in the game by a sand icon (see the image above).
Other lesser known methods of obtaining Ash include purchasing the Wretched Broker. This merchant is unlocked after you perform the "Summoning of the Mercantile Fortune" Incantation at the Concoct. It requires x10 Bones to craft the Incantation, so make sure you have enough. Once the Wretched Broker appears on Crossroads, you can buy x1 Ash for x15 Bones in Hades 2.
To use Ash, you must visit the Altar of Ashes in Crossroads. This location is unlocked after your first death in the game. Once you die, you can go to the Altar of Ashes and spend the specified amount of Ashes to purchase an Arcana card there. Each card provides a buff that can be equipped or disabled at will.