In League of Legends, Senna is a Support/Marksman, which left a lot of people worried that we were looking at another zoner. To be fair, that is what Riot themselves classify her as:

However, the connoisseurs among us have one thing to say:
Welcome home Unika from GGST.

Senna’s gameplay reveal trailer can be seen below and you’ll be able to release her from Thresh’s lantern yourself on June 9th

Senna is the 2nd character to join 2XKO’s roster and the last from their roadmap and look ahead earlier in the year: 2XKO: What’s Next + New Champs
Hopefully this isn’t the last character to be released but with over half the development team being laid off, that remains to be seen.