I was able to procure my Vault level 21 doing today’s Dr T event for my main account. I believe it should be ready by the time the Mega Crab event goes on so that I can focus all resource efforts for an Landing Craft level 23.
It shocks me whenever I see a base with a low level Vault, especially around my HQ level. One of the top priorities whenever you level is to maximize your Vault immediately. Why? Because it’ll minimize how much an opponent can damage you.