You can use spells crafted with a Mastery focus to apply a Mastery debuff to enemies. This debuff can be applied infinitely and only dissipates when you consume it (through a spell that consumes Mastery, such as damage from Destruction spells or stored damage from Control spells), or when the enemy dies.

Mastery is the key to achieving big damage numbers and spectacular Overkills. When thinking of Destruction, Control, and Mastery, think of Destruction as a hammer, Control as an anvil, and Mastery as a spike. Swinging a hammer on its own will do damage, but using an anvil will help you line up your strikes. If you hold a spike in front of the hammer, the damage of your strike will be amplified. Using all three in conjunction is a skill that leads to efficient kills, but a spike on its own is not the most effective weapon.

A simple way to use Mastery is as follows: Craft a Targeted Lightning Mastery spell and cast it against an enemy several times. Now use a charged critical cast of a Destructive Fire spell against the enemy. Depending on the properties of your Fire spell, a certain amount of Mastery will be consumed and applied as an additional critical damage bonus to the enemy, resulting in much higher damage than you would have seen with the Fire spell on its own.

Mastery does not damage enemies, but most Mastery spells do apply secondary effects. For instance, Fire Mastery spells apply a Burning Aura, which applies burning damage to nearby enemies.

Careful use of Mastery can be used to achieve more efficient kills and also Overkills, which can charge Synergies if you have them equipped. Note that consuming Mastery does not always do damage. In some cases it enhances other critical effects. Experiment with Mastery versions of all your Sigils to see the effects.

Overkills are achieved when you apply more damage than is necessary to kill an enemy. If your Overkill is powerful enough, you will see a Sigil-specific death effect on the enemy you just killed. All points of Overkill damage are applied to charging any Synergies you have equipped, provided that the other necessary conditions are met.

Apocalypticals are special events that periodically occur when you strike an enemy with a charged Critical cast of a spell. Apocalypticals apply bonus damage and effects to enemies, and mark them as Sigil Power targets.

Synergies are powerful spells that can be cast only when two Sigils interact. Synergies require a deep understanding of the crafting and combat systems, as well as a large volume of high-rarity items.

Synergies manifest as affixes on Unique Spells. To access a Synergy, you must first create a Unique Pattern. You can do this by using the Synthesis Upgrade menu to Upgrade a Legendary Pattern with two Legendary items. The resulting Unique Pattern will have a random Synergy affix.

Once you have a Pattern that contains a Synergy in your Inventory, you must craft it into a spell with the Sigil specified in the Pattern description (the Primary Sigil). Next, equip your Synergy-affixed Spell.

In order to use the Synergy, you must have both of that Synergy’s Sigils equipped. (The required Sigils are specified in the Spell’s description: the Primary Sigil and Secondary Sigil). With the spell and both Sigils equipped, you can now charge the Synergy.

To charge a Synergy, use either of the Synergy’s Sigils to tag an enemy with any spell. When a tagged enemy is killed, any Overkill damage is applied to the Synergy’s charge meter, which can be found in the Spell Bank of the Primary Sigil. If you tag the enemy with both of the Synergy’s Sigils before killing the enemy, a bonus charge is applied to the meter, allowing you to cast Synergies more frequently.

Once the Synergy charge meter is fully, the Synergy is ready to cast. To cast the Synergy, cast the AOE spell from the Primary Sigil.

Sigil Powers are special spells that can be cast only when Apocalypticals occur. Each Sigil has its own unique Sigil Power, which improves as you Upgrade that Sigil.

To cast a Sigil Power, wait for an Apocalyptical to take place. Apocalypticals are rare, but you can improve their chances by frequently casting charged critical spells and by crafting with Items that have Apocalyptical-based affixes.

When an Apocalyptical happens, the enemy is tagged with a Sigil mark. If the enemy is killed before the mark dissipates, the Sigil Power goes into effect. Different Sigil Powers are used in different ways. Some appear instantly when the enemy is killed; others are imbued in a certain spell, such as the Nova or Targeted spell for that Sigil.