Kelton - the Great Sage, who holds the title of High-Sage, is a level 87 Great Mage who can use 8th-tier magic along with 8th-level or higher skills.
Walton - the Great Swordsman titled Infinite Blade is an Lv.89 Swordsman who has at least 5 Sword Skills above Lv.8 of A rank and one Sword Skill above Lv.5 of S rank.
Melos - the Great Summoner, who holds the title of Beastmaster, is a level 85 summoner. Though almost the same as a mage, summoners are of a very different nature. They naturally summon beasts or monsters to fight in their stead. Melos in particular had signed deals with many strong beasts, some of which were in Lv.90s.
So these three together might have a chance to defeat Shin - at least that's what Balton thought and after much deliberation came to that conclusion.