Seo "Soul" Hyeon-seok joined the new Prime Clan early in 2015 as their top laner. They qualified for SBENU Champions Summer 2015 after going 1-1 in their group against Samsung Galaxy and Xenics during Champions Summer 2015 Promotion. Afterwards, Prime was sponsored by SBENU and renamed themselves to SBENU Sonicboom. Halfway through Champions, SoaR joined SBENU to share the starting top lane spot with Soul. SBENU placed last in Champions Summer and were forced to play in the LCK 2016 Season Spring Promotion. SBENU played Ever and managed to win 3-1 to requalify for the LCK.
SBENU played in the 2015 LoL KeSPA Cup where they lost 2-1 in the quarterfinals to SK Telecom T1. Soul did not play in this tournament.
During the 2016 LCK Spring Season, SBENU Sonicboom went 2-16 in sets, finishing in ninth place, forcing them to play relegations matches for their spot in the summer split. SBENU chose ESC Ever as their relegations opponent, but were defeated 3-0, relegating them to Challengers Korea 2016 Summer.