Load screen tips and some abilities mention that they set up combos. Do combos depend on elemental types involved or can any type combo with another type? Do any special effects happen other than increased damage?
Each Primer ability usually inflicts a negative status effect to an enemy or group of enemies, such as ice (slow/freeze) or acid (DoT). Once an enemy has a Primer ability applied to them, the next Detonator ability that hits that enemy will execute the detonating Javelin's combo effect. This will not stop the status effect from the Primer ability. In order to detonate another combo on that same enemy, the enemy will need to be hit with another Primer ability, even if they are still under the status effect from the previous Primer ability.
Some Primer abilities take time before the enemy becomes detonatable. There is an icon that appears over each enemy when they are Primed and ready for detonation. The icon is a small hexagon that depends on the elemental type of the Primer Ability: Ice, Fire, Acid, or Lightning.
In the UI, Primer abilities are marked in the Forge customization window with a circle icon, and Detonator abilities are marked with a star.
Some abilities are neither Primers, nor Detonators, and some abilities (Elemental Storm) are both.
Javelin Combo Effects
- Ranger -- Critical Target Damage: Detonating an enemy causes more damage than any other Javelin's detonation
- Colossus -- Explosion: Detonating an enemy causes an explosion which damages all nearby enemies
- Storm -- Spread: Detonating an enemy causes an explosion which spreads the enemy's elemental status effect to nearby foes
- Interceptor -- Aura: Detonating an enemy causes its elemental status effect to become imbued into your Javelin, which can then be spread to nearby targets through proximity
This info was summarized from Gamespot.