Seal Knight is one of the three skins released under the Morgana's Castle offer. It could be individually purchased using game coins in March 2017.
Seal Knight could be purchased in the Skins Shop under the 'Excalibur' tab for 1990 coins. It was available for a limited time and may not be available for purchase in the future.
Details of this offer can vary depending on location, platform or time.
Note: The Morgana's Castle offer has been released many times after the initial debut in 2017. The last three limited times releases were in October 2021, January 2022 and then in April 2022. The price for Seal Knight remained at 1990 coins for each release of these releases.