The advantage on attacks in dim light or darkness just enhances the weapon on its own.

The finesse, light, and thrown properties allow it to be versatile in combat. The 2d8 damage is psychic and rivals any standard weapon. Shadow Blade allows the caster to create a weapon spontaneously and instantly gain proficiency with it. The ability to instantly arm yourself with a blade of pure shadow as a bonus action is never going to be a bad thing. It also has the ability to be cast at higher levels meaning its usefulness will continue on with the character. The automatic proficiency and additional damage in dim light or darkness make the spell a decent choice for level 2. The rules for Shadow Blade provide a good description of what the blade looks like and how it functions. When you cast it using a spell slot of 7th level or higher, the damage increases to 5d8. When you cast it using a 5th- or 6th-level spell slot, the damage increases to 4d8. Thereafter, while the spell persists, you can use a bonus action to cause the sword to reappear in your hand.ДЄt Higher Levels: When you cast this spell using a 3rd- or 4th-level spell slot, the damage increases to 3d8. If you drop the weapon or throw it, it dissipates at the end of the turn. In addition, when you use the sword to attack a target that is in dim light or darkness, you make the attack roll with advantage. It deals 2d8 psychic damage on a hit and has the finesse, light, and thrown properties (range 20/60). It counts as a simple melee weapon with which you are proficient. This magic sword lasts until the spell ends. You weave together threads of shadow to create a sword of solidified gloom in your hand.

Can You Give the Shadow Blade to Someone Else?.

Does Sneak Attack work with Shadow Blade?.

Does Booming Blade work with Shadow Blade?.

5e shadow blade build