The Floor is Lava

You cause the ground floor within one room of a humanoid dwelling, in which you occupy, to become a magical facsimile of molten lava. This lava floor spreads around inanimate obstacles and supports objects, and furniture without damaging them. For the duration the floor is considered difficult terrain.

A creature making contact with the floor when the lava appears can make a Dexterity saving throw to pull themselves onto a raised platform it can reach, thus avoiding the lava. On a failed save the creature takes 5d8 fire damage. A creature takes the same damage if it touches the floor for the first time on a turn or ends its turn there.

When the spell ends the lava vanishes as if it never appeared.

At higher levels. When you cast this spell using a spell slot of 6th level or higher, the damage increases by 2d8 and the lava can spread to one additional room in the structure per spell slot above 5th.