You summon a blade of chromatic energy, manifesting as a sword of acid, cold, fire, lightning, poison, or thunder (chosen when cast). This magic sword lasts until the spell ends, counting as a simple melee weapon with which you are proficient. It deals 2d8 damage of your chosen type on a hit and has the finesse, light, and thrown properties (range 20/60). In addition, you have advantage when using the sword to attack a target that is resistant to the blade's chosen damage type.
If you drop the weapon or throw it, it dissipates at the end of the turn. Thereafter, while the spell persists, you can use a bonus action to cause the sword to reappear in your hand.
At Higher Levels. When you cast this spell using a 3rd- or 4th-level spell slot, the damage increases to 3d8. When you cast it using a 5th- or 6th-level spell slot, the damage increases to 4d8. When you cast it using a spell slot of 7th level or higher, the damage increases to 5d8.
This is a straightforward chromatic version of Shadow Blade, allowing the caster to summon a blade of acid, cold, fire, lightning, poison or thunder.
Due to the flexibility of being able to choose the damage type, its advantage condition is intentionally a trade off, as it requires the target to be resistant, so without any further bonuses you will be choosing between full damage or advantage with half damage (useful if your chance to hit is poor, as half damage is better than none). However, it is also possible to combine this spell with Elemental Adept if you wish to deal full damage using a specific element (as the target only needs to have resistance, it doesn't matter if it is bypassed or not); this makes it possible to double down on acid blade for an acid-focused sorcerer, for example.
I've given this spell fairly broad access across single attack spellcasters, including the Alchemist Artificer sub-class (who could do with a boost if you want to be more of a fighty alchemist, and because acid and poison are on brand). I've also applied it to Arcane Trickster, though it being available to Wizard might render that redundant (I'm not sure), I like to have more elemental options as while Shadow Blade is ideal for a classic trickster, it's less suitable for more unusual builds who might prefer other elements.