The Blackout (2009) on Netflix

Plot summary

Christmas Eve finds only a handful of tenants left in The Ravenwood when a blackout takes down the whole city. With the power gone, the residents are stuck inside the building. Tremors have opened fissures in the ground, and something has come out of them: small creatures, part mollusk and part tiny armadillo, that grow at a rapid rate into alien-looking things with a lethal tail. The creatures move through the floors, and the tenants are stalked and attacked. Elizabeth Pierce, Daniel Pierce, Dylan Pierce, Ethan Devane, Claire Devane, Freddy Appleton, Eddie Clifton and their neighbors have to work together to get out and survive the night.