The Hybrid Blade (5e Equipment)
From D&D Wiki
Weapon (any sword), legendary (requires attunement)
This magical weapon has a +2 bonus to attack and damage rolls.
The user may change the hybrid blade's damage it deals and must declare it upon first use. The weapon regains this effect at dawn.
This weapon does half of it's damage as one magic damage, and half of it's damage as the other selected type.
Examples include but not exclusive to: Cold, Fire, Lightning, Radiant, Necrotic, Poison, etc..
NOTE: If Necrotic is one of the two enchantments chosen Radiant cannot be the other choice, such as Fire and Ice cannot share the effects at the same time. If the chosen enchantments on the blade counter each other the blade does normal slashing damage instead of magic until after a long rest/ next dawn.
Example 2: Blade does 1d8 before enchanting, the magic replaces blade damage. Placing half the damage upon each magical enchantment. Aka 1d4+1d4 instead of 1d8