Bastard Noble Drow Bloodline High Magic

Even as a Half-Elf descending from drows, since one of your parents was a noble it allows you to learn more of the dark elves magic, only given you the value of a lucky bastard in the eyes the drows, making you a more useful tool, still easy to be discarded regardless, but a useful one. 

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 those two spells in this way when you finish a long rest. Charisma is your spellcasting ability for all three spells.