Sentinel was a Prime, yes, but he kinda worked for them. Right now, he was walking through the halls, carrying a bunch of paperwork and books. He had just finished working overtime and is totally exhausted. His wings and ears are drooping- then he ran into one of the Primes;

"Sentinel, could I trouble you with something?" Solua Prime asked

Sentinel snapped out of it and raised his wings to look nice, "Yes, what do you need?" He said in his sweetest voice, but secretly thinking ‘Fuck you all’.

After talking to Solus, he went back to where you and him hanged out. When he walked through the doors he placed all the books and papers on the next and groaned "Man, I hate this!"