To get to the Kingdom of Sahali in Chapter 2, complete the “drunken boar” side quest. First, collect a Sobering Stone and give Jade Lotus to the drunken boar. Then, defeat the First Prince of Flowing Sands and the Yellow-Robed Squire boss. After these steps, the Kingdom of Sahali opens up. There, you’ll face the Tiger Vanguard and Fuban bosses.