Okay so this is my OTP and I’m complete garbage when it comes to anything Twilight and Tempest related  
But okay, some backstory on this is that I headcanon that after Tempest spread the defeat of the Storm King beyond Equestria, she came back to see the Mane 6 again, but more specifically, Twilight. Since the Mane 6 have defeated countless villains, there’s a huge bounty on their heads, but mostly Twilight, since she’s sort of the “leader” of the group. To repay Twilight for saving her life and showing her that hope exists, Tempest requests to be Twilight’s personal body guard in her castle. Twilight accepts without question. While they both have crushes on each other, Tempest’s is super strong and Twi’s better at hiding hers.  
This sketch is later in time when Tempest defends Twilight’s castle from a timberwolf attack, and Twi’s not hesitant to get up close to thank her. Tempest takes this as a sign, but for now they haven’t figured out they like each other.  
Twilight’s got streaks of yellow/gold in her mane from that Rainbow Power, because as she ages she starts to appear more alicorn-like and takes a very “twilit night” sort of appearance (like Luna and Celestia in their respective elements). Her wings also change to resemble the Rainbow Power’s colors.  
Tempest’s cutie mark is a milkshake, but she’s got the Storm King’s symbol over it because it was branded onto her when she decided to join forces with him. It’s fading, and Twilight’s working on a way to get rid of the scar. Had her destiny not been interrupted, Tempest and Pinkie would’ve probably been great friends ^_ I might explore that Tempest concept further, but for now, this is TempeTwi.  
Thank you for stopping by to take a look! As always, feedback is definitely welcome and very appreciated!