SAN FRANCISCO — Last spring, the Federal Home Loan Bank of San Francisco hit a whole mob of financial institutions with a lawsuit demanding money back for residential mortgage-backed bonds gone bad. In the summer, Charles Schwab & Co. followed suit.

In the intervening months, JPMorgan Chase & Co., Merrill Lynch, Credit Suisse and other defendants have hired a diverse crowd of lawyers — including some recognizable local names — showing how seriously they’re taking the opening salvos in litigation with potential billions in exposure.