Ye-dam, Ji-hoon and Do-young made their first appearance together on Mnet survival program Stray Kids on November 21, 2017 as representatives for the label. Within the same timeframe, Hyun-suk and Jun-kyu appeared on JTBC survival program Mix Nine. Both finished in 5th and 35th place respectively. In the following year, YGE unveiled 29 trainees through survival show YG Treasure Box on November 17, 2018. Notable trainees included Bang Ye-dam from K-pop Star 2, Mix Nine contestants Choi Hyun-suk and Kim Jun-kyu.
During the finale, Haruto, Ye-dam, Jung-hwan and Jun-kyu were the first to join the final line-up, followed Jeong-woo, Jae-hyuk and Hyun-suk, under the group name Treasure. In January 29, 2019 an announcement for a second line-up was reported. The members were disclosed to be Yoon-bin, Mashiho, Do-young, Yoshinori, Ji-hoon and Asahi under the name Magnum. Both groups were collectively to be called Treasure 13, with official fandom name Treasure Maker, derived from the name viewers were given of YG Treasure Box.
Prior to debut, a series of promotional posters for the group were released from April 29, 2019 onward. On episode 2 of labelmate Kwon Hyun-bin’s reality show Kwon Hyun-bin Begins, Haruto and Hyun-suk made a short appearance, followed appearances by Jun-kyu, Ye-dam, Hyun-suk, Jung-hwan and Haruto on episode 3.