Source: Xanathar's Guide to Everything

Prerequisite: Elf (drow)

You learn more of the magic typical of dark elves. You learn the Detect Magic spell and can cast it at will, without expending a spell slot. You also learn Levitate and Dispel Magic , each of which you can cast once without expending a spell slot. You regain the ability to cast the spell in this way when you finish a long rest. Charisma is your spellcasting ability for these spells.