Elixir of Darkness

After discussing their course of action, Winter left the small shop and headed toward the Blood City instead of starting with the All-Devil City. She chose to target the city of hunters because it would divert the attention from Ace in All Devil City. 

As for Ace, he closed the shop and used his Qi to dig an underground chamber before sealing it with all sorts of formations. Once he was done, he opened the system shop and bought the Elixir of Darkness for 50 million TP, which he was putting up on hold up until now. 

He didn't dare to use it before because its effect was unknown, and he still needed to chase after his target. He was waiting for this kind of opportunity to arise, and now that his targets were literally immobilized, he didn't need to worry about anything.