Here's how to add abilities to the feats in D&D Beyond:
*Shadow Manipulation Feat*
1. Access the Shadow Manipulation feat.
2. Click "Edit" and scroll to "Benefit."
3. Click "Add Ability."
*Ability 1: Shadowy Illusions*
1. Ability name: Shadowy Illusions
2. Ability description: Create a 10-foot radius of magical darkness...
3. Ability type: Area Effect
4. Effect: Enemies within the area have disadvantage on Wisdom (Perception) checks.
5. Duration: 1 minute
*Shadowblade Feat*
1. Access the Shadowblade feat.
2. Click "Edit" and scroll to "Benefit."
3. Click "Add Ability."
*Ability 1: Force Damage*
1. Ability name: Force Damage
2. Ability description: Melee attacks deal an additional 1d6 force damage...
3. Ability type: Melee Attack
4. Damage/Effect: 1d6 adow Dagger Attack*
1. Ability name: Shadow Dagger Attack
2. Ability description: Make a melee attack with a shadow dagger...
3. Ability type: Melee Attack
4. Damage/Effect: 1d6 + Dexterity modifier piercing damage
5. Target/Area: Single target
*Ability 2: Shadow Dagger Defense*
1. Ability name: Shadow Dagger Defense
2. Ability description: Use a shadow dagger to deflect an incoming attack...
3. Ability type: Defensive Ability
4. Benefit: Advantage on one Dexterity saving throw
5. Target/Area: Self
*Ability 3: Shadow Dagger Distraction*
1. Ability name: Shadow Dagger Distraction
2. Ability description: Create a cloud of shadowy daggers...
3. Ability type: Area Effect
4. Effect: Distract enemies within 5 feet
5. Duration: 1 minute