In 2018, when the League of Legends World Championship final was being played in South Korea, K/DA Kai'Sa was introduced to the community as the first Prestige Skin. Swapping its purple outfit for a more golden and sparkling on, the Prestige version of K/DA Kai'Sa could be obtained against 2500 tokens from the Worlds in-game event.
Since then, these prestigious versions have become commonplace for many appearances. The only way to unlock these skins is to earn prestige points via missions, points that are very difficult to obtain without the famous passes available during the various events.
This system has been adjusted over the months. Now, you need to accumulate almost 100 prestige tokens to get the alternative — and deluxe — version of your favorite champion's skin. The only thing you have to do is to play the different missions available during the event, especially if you bought the related pass. You'll have then a greater chance to unlock the Prestige Skin associated with this event. A few weeks after the event, it won't be possible to get it anymore.
Design Lead Xenogeci returned to this system on a long twitter post, and explained that Riot Games believed that Prestige Skins associated to the past two events — Mecha Kingdom and Night & Dawn events — were too easy to obtain.
For previous events, Riot Games had calculated that it would take about four matches a day to unlock the prestige version if you bought the pass. The players felt that it was too much, so the studio had decreased to three games — then one and a half outside of school holidays to help the players.
As a consequence, the studio decided that the Prestige skins associated with the Galaxies event would require more effort from players to unlock them. It has been calculated that it would take two to three games a day with the pass to unlock them.