Please keep in mind that Scrolls is still in beta, and that as the game is updated these damage types might be changed.
Hello and welcome to a rather short guide in which I hope to adequately outline the damage types and relevant interactions in Scrolls.
There are primarily four damage types which I will go over:
In Scrolls, there are a number of hidden "phases" each turn goes through, but for the purpose of this guide you only need to be aware of one - the Combat phase. The combat phase begins when you press the end turn button, and ends right as your turn ends. This is important to know, as the damage dealt by the attacking units as well as the defending units (through the Spiky-trait) is treated as Combat damage which can be reduced by the Armor trait (which reduces combat damage by X, where X is the Armor value.) Furthermore, Combat damage dealt by units can be increased through the use of Curse, which increases the damage taken by the Curse value.
Everything outside of the Combat phase is therefore not combat damage, and there are two primary damage types to keep in mind. First off is non-combat damage, which is any non-typed damage dealt by either spells, enchantments, or even units outside of the Combat phase. When it comes to spells, we have Violent Dispersal as an example of a non-combat damage dealing spell; for enchantments, Ember bonds; and there's even units that will deal non-combat damage (via abilities), such as the Sinmarked Zealot and the Hired Marksman. Just as combat damage can be reduced by Armor, non-combat damage can be reduced by Magic armor.
The cousin to non-combat damage is poison damage, primarily found in Decay (with a couple of Growth scrolls being the exception), which works very much like non-combat damage in all but one aspect - Poison damage can be increased by Curse much like Combat damage. Poison damage is primarily dealt to units through the Poisoned status effect, which deals 1 poison damage at the beginning of every turn, but there are enchantments as well as units that will deal poison damage such as the enchantment Infectious Blight, and the Blightbearer which deals 1 poison damage to itself at the start of the Combat phase. Like non-combat damage, poison damage can be reduced by Magic armor, but unlike non-combat damage poison damage is also affected by Curse.
The final damage type can be found on Scrolls that deal self-inflicted damage (to see all the scrolls utilizing pure damage, search in the deck builder using the "d: pure" search modifier), which can neither be reduced nor increased by the likes of Curse, Armor, or Magic armor.
It pays to keep up to date on the damage types and damage interactions in Scrolls, so that you're absolutely sure just how much damage will be dealt and taken by units. I hope this short guide will be helpful in your future adventures in Scrolls!
Sysp explains some of the nuances behind card sacrificing.