In the debut season, the Locke children find a total of 12 magical keys — including but not limited to the Anywhere Key, Mirror Key, Matchstick Key, Head Key, and the all-powerful Omega Key. In Season 1, Tyler Locke (Connor Jessup) also found the Echo Key — which has certainly come in handy since then.
The cast discovers another eight keys in Locke & Key’s sophomoric season, and in Season 3, they found the final four.
Source: https://www.distractify.com/p/how-many-keys-are-in-locke-and-key