Use your favourite features in-game with our Desktop AppIgnite is a Damaging Elemental Ailment that deals Fire Damage over time by default, and is typically inflicted by a Hit. The base Damage dealt by Ignite only accounts for the total Fire Damage in a Hit. Ignite does not stack by default and only the highest Damage Ignite on a target will deal its Damage. However, all inflicted Ignites will be present on a target and will remain for their full Duration, with the next highest Damage Ignite dealing its Damage once the current one expires.
Any Fire Damage in a Hit will inflict Flammability based on the total Fire Damage dealt. Flammability is a Debuff associated with Fire Damage and Ignite which provides a chance for incoming Fire Hit Damage to Ignite the target. However, the exact chance to inflict Ignite is based on Flammability Magnitude.
Flammability lasts for 4 seconds by default, but each Hit of Fire Damage will effectively 'stack' Flammability Magnitude and refresh the Debuff Duration. Therefore if you're Hitting a target regularly enough with Fire Damage, it's possible to maintain Flammability and raise its Magnitude to 100%, allowing all incoming Fire Damage Hits to Ignite the target.
Note: Flammability is not a Curse.
Some Skills or Unique items have special modifiers that interact with Ignite chance, such as 
Black Powder Blitz which has the modifier 'Always Ignites'. This modifier bypasses the chance to Ignite calculation, but can still only Ignite with Fire Damage by default.
The default Magnitude of Ignite is 20% of the Fire Damage of an Igniting Hit, dealt as Fire Damage per second. Modifiers to the Magnitude of Ignite, such as 'increased Magnitude of Ignite you inflict', are multipliers to the base Magnitude. For example with '25% increased Magnitude of Ignite you inflict', your Ignites will deal 25% of the Fire Damage of an Igniting Hit per second (20% * 1.25 = 25%).
Note: modifiers to Magnitude do not affect Ignite Duration.
The Damage dealt by Ignite only accounts for the total Fire Damage in an Igniting Hit by default. The final Fire Damage dealt by a Hit prior to the target's mitigation will determine how much Damage is dealt per second. This is inclusive of any relevant Damage modifiers you have such as 'increased Fire Damage', or if the Hit was a Critical Hit, but does not include any modifiers that specifically apply to how much Damage the target takes from the Hit, such as Penetration.
The default Duration of Ignite is 4 seconds and can be increased with modifiers to Ailment duration such as 'increased Ignite Duration on Enemies' or 'increased Duration of Damaging Ailments on Enemies'. Increasing the Duration of Ignite will improve the total Damage dealt across the full duration of the Ailment, but not the Damage dealt per second. Modifiers that make an Ailment deal Damage faster will cause the Ailment to deal its total Damage over a shorter period of time, essentially increasing the Damage dealt per second.
Since your Damage modifiers are factored in when calculating the base Damage of an Ignite, they won't apply a second time directly to the Ignite itself. Therefore modifiers that improve the Magnitude of Ignite are exceptionally powerful in scaling Ignite Damage as they essentially function as direct Damage multipliers. For example 
The Searing Touch has '100% increased Magnitude of Ignite you inflict', which alone would double the base Magnitude, and thus Damage, of Ignites you inflict.
Another way to scale Ignite Damage is with modifiers that increase the amount of Damage the target takes from Ignite. For example, by lowering their Fire Resistance with Elemental Weakness or Exposure, or by inflicting Shock which makes them take increased Damage from all sources.
The Infernalist Witch ascendancy has access to the 
Bringer of Flame notable that provides the modifier 'All Damage from you and Allies in your Presence contributes to Ignite Chance and Magnitude'. This modifier changes the Ignite calculation for both applying Flammability and the Magnitude of Ignite to also include any non-Fire Hit Damage, providing the powerful option of being able to Ignite with non-Fire based Skills. All of the Damage in a Hit is summed and used to calculate the Magnitude of the inflicted Flammability Debuff and any resulting Ignite.
The 
Blackflame Unique Ring has the special modifier 'Enemies Ignited by you take Chaos Damage instead of Fire Damage from Ignite'. Importantly, this modifier only changes the Damage type that the target takes from your Ignites, not the Damage used to scale Ignite on your character.
All of the normal modifiers that would scale an Igniting Hit, such as 'increased Fire Damage', still apply in regards to scaling Ignite Magnitude. However, scaling the Ignite Damage with modifiers on the target instead requires modifiers that would increase the amount of Chaos Damage the target takes, such as 
Despair or Withered.
Blackflame Covenant is a Keystone that converts 100% of your Fire Damage from Fire Spells into Chaos Damage. It also allows this Chaos Damage to inflict Flammability and contribute to Ignite Magnitude. However, unlike the 
Blackflame Unique Ring discussed above, this Keystone will cause your Ignites from Fire Spells to deal Chaos Damage over time instead of Fire Damage over time - this means that your Damage scaling vectors that specifically apply to Fire Damage, such as 'increased Fire Damage', will no longer scale the Hit and therefore also no longer scale the Ignite. Instead you'll need modifiers that apply directly to Chaos Damage scaling, such as 'increased Chaos Damage'.
