Only appears after you have won a game of Tactical Defense. Speak to him quickly, he is only there for 2-3 minutes.
He doesn't spawn immediately after BZ dies, can take a minute or two, but spawns next to where the Coin guy is at.
Lore & Dialog
Supreme Tactician tells you, "Congratulations! Only a worthy combatant could survive all those monsters. Take this token as a reward.
Supreme Tactician gives you Society Treasure Key.
Supreme Tactician gives you Celestial Hand Trade Token.
"You have been granted the Title "Tactical Aid"."