Dark Blast is a Primary Power Set for Blasters and Corruptors and a Secondary Power Set for Defenders.
You can tap into the power of darkness and draw forth its necrotic energies. This power can be used to damage foes and inhibit their perceptions, as well as drain their very life energy for your benefit. The source of your access to the netherworld may be magical, biological, some form of strange or alien technology, or you may not even know how you do it.
Some Dark Blast features require an attack roll. In all such cases, you are making a ranged attack that you are proficient with, and you add your Dexterity Modifier to the roll. You also add your Dexterity Modifier to the damage.
You can emit a blast of dark energy toward a creature that you can see within 80 feet. Use your Action to make a ranged attack roll. This blast deals necrotic damage equal to 2d6 plus your Dexterity Modifier, and you can add Endurance Dice to the damage roll. The target must make a Constitution Saving Throw or suffer disadvantage on all attack rolls it makes until the end of its next turn. You can also shoot a Moonbeam at 1st level or at 3rd level if you are a Blaster.
The darkness within you can be brought forth through your eyes -- a stare that has swallowed countless souls. You can use your Action to capture the gaze of a creature you can see within 70 feet. That creature must make a Wisdom Saving Throw or be caught up in your unearthly power. Once you have its attention, you can maintain your Netherworld Gaze on your target on subsequent turns without requiring that your target repeat its Saving Throw. However, you must maintain concentration and you can only apply your Gaze to one creature at a time. It finds itself unable to look away and suffers disadvantage on Dexterity and Wisdom Saving Throws, although it is free to move and act as normal. If your target takes damage of a type other than necrotic, becomes unconscious, blinded, or otherwise unable to see you, moves out of range, or you lose sight of it, this feature ends immediately.
You can use the following features on a creature held in your Gaze: Gloom at 1st level and Life Drain at 10th level if Dark Blast is your Primary Power Set or at 14th level if it is your Secondary Power Set. If you are a Blaster, you may also use Abyssal Gaze at 7th level.
At 1st level if you're a Blaster, or a 7th level if Dark Blast is your Primary Power Set and at 11th level if it is your Secondary Power Set, you can use your Action to release a wave of necrotic energy outward from you in a cone 60 feet long and 30 feet wide. Each creature in that area must make a Dexterity Saving Throw or take 1d8 necrotic damage and suffer disadvantage on all attack rolls until the end of its next turn. You may add one or more Endurance Dice to this damage. If the creature is Large or smaller and fails its Saving Throw, it will be moved 30 feet away from you and be knocked prone. If a creature's Saving Throw is successful, it takes half damage and is moved 15 feet from you (size permitting) but ignores the other effects.
You may use Tenebrous Tentacles at 4th level if you are a Blaster, or at 3rd level if Dark Blast is your Primary Power Set and at 6th level if it is your Secondary Power Set. You can use Night Fall at 4th level if you are a Corruptor and at and 8th level if you are a Defender, but it is not available to Blasters.
At 2nd level if if you are a Blaster, you can use your Bonus Action to take a moment to focus your senses. Roll at least one Endurance Die. You can add the result to every Dark Blast attack and damage roll you make until the end of your next turn. This feature not available to other Archetypes. Using this feature does not cost an Action but you can only do it on your turn.
At 2nd level if Dark Blast is your Primary Power Set or at 4th level if it is your Secondary Power Set, you can use your Action to select a location that you can see within 70 feet. Each creature within 20 feet of this spot must make a Constitution Saving Throw or be stunned until the end of its next turn. This feature is not available to Blasters.
At 12th level if Dark Blast is your Primary Power Set and at 15th level if it is your Secondary Power Set, you can use your Action to release a massive burst of netherworld energy out from yourself. You must roll at least half of your available Endurance Dice, and if you use more than half of your maximum you may also re-roll any Endurance Die that comes up a 1 or 2 (but you must use the new value). Each creature within 25 feet of you must make a successful Constitution Saving Throw or suffer twice the rolled amount of damage, half as necrotic and half as bludgeoning. A creature that makes a successful Saving Throw receives half of the rolled damage only as necrotic. Regardless, each creature in range also suffers disadvantage on all attack rolls, Dexterity Checks, and Dexterity Saving Throws until the end of its next turn. You are not affected by this feature.