In Star Wars Zero Company, your main operators will come to you and ask for help. This triggers their companion missions, and usually involves lending them a hand, helping them confront something from their past.
Tel-Rea, the young padawan you meet early on in the game, is no different. After a big story moment that I will spoil below (click away if you're not there yet! You'll know it when you see it), Tel will come to you, asking you to go with her to Dantooine. Accept, and start the quest Sisters.
Spoiler warning for a major main story moment in Star Wars Zero Company
Tel will only come to you with this offer after Order 66 has happened, and you've been through the timeskip. She's received an invitation to meet on Dantooine from a Jedi she used to be friends with: Trilla.
If you've played Star Wars Jedi: Fallen Order before, this will raise alarm bells. Needless to say, this will not be a straightforward reunion - prepare for combat.
You should get access to the mission after Deep Cover has been completed. For me, it triggered on Cycle 30.
This mission is all about survival. Additionally, it's even easier to lose Tel during the mission, because she can be killed after being downed just once.
For that reason, you should think carefully about your team. Hawks and Tel are mandatory. I would recommend bringing a medic, too - especially one who can dish out lots of healing in a single turn. Otherwise, consider someone who can chip away at weaker enemies surrounding the boss, like Cly.
سەرچاوەی فەرمی بە زمانی ئینگلیزی: https://www.thegamer.com/star-wars-zero-company-trilla-second-sister-boss-fight-mission-guide/
