Board Thread:General Discussion/@comment-50.244.4.150-20161229052342/@comment-27794543-20161229072519

Lexa was Heda for the entirety of the first season – we just never saw her. Season 1 was literally a month before season 2 (according to timeline clues, season 1 was 13 September – 11 October 2149 and season 2 was 12 October – 3 November 2149). Lexa became Heda a few years before season 2, meaning a few years before season 1. As for who was Heda before Lexa, that's unknown.