Houses do not rule planets.
Planets rule signs
and a sign ruled by a particular planet appears on the cusp of some house.
The planet that rules the sign on the cusp of a house is lord of that house, its ruler.
The ruler of a house has dominion over the affairs of the house
and of any planets found within the boundaries of the sign it rules.
Whether the ruler operates for good or evil depends on its conditioning
for which there are many measurements.
A planet in a house operates most strongly there because directly,
although its behavior is determined by its ruler, even though indirect.
Rather than "ruler"
we might say that the planet ruling the sign on a cusp "disposes" that house
and whatever it contains.
Houses are fixed in relation to Earth.
They are earth-bound, or mundane, and symbolize "surrounding circumstances".