Slake is an item that allows the user to learn Rigos' skill. It was one of the rewards given for defeating Rigos.[1]
It was given to Tac by Hardcore Leveling Warrior after Rigos was defeated in the Subjugation Round.[1]
Image Gallery
HCLW getting the rewards from defeating Rigos in the Subjugation Round. One of the rewards being the Slake skill (Episode 44)
Tac receiving Slake form HCLW (Episode 44)