Need help with new character

Hi! I'm unsure if this is the right channel. It seems like the best out of a quick scroll through.

I'm trying to create a nullification knight. The idea for the character is based around such: wizards outclass knights in most general fantasy contexts. So, what if there was a knight who could learn the right magic and seek out the right knowledge to be able to deflect and diffuse all harmful, incoming magic?

Sure, against another knight, they're just another knight. But to a wizard who may be less skilled with a sword and less armored- that sounds rather scary.

Imagine it: a whole army is being burnt, shocked, poisoned, sent on illusory trips. Then one knight is just walking straight through the fire, straight through everything the evil wizard is throwing at them. And in one fell swoop, the problem is dealt with.

Only problem is I'm new to DND and I need to find the right race, class, and spells. Any help?