Invader (noun)

1. A person or group that enters another's territory and establishes control.
2. A person or thing that intrudes or impinges on another's property or rights.

Origin:

Late 16th century from latin invadere "to fall upon", from in- "into" + vadere "go".

Examples:

1. The invaders from the north burned down the town.
2. The invader caused significant harm to the crops.
3. The invasion was launched at dawn.
4. A group of aliens landed and were taken as invaders.
5. The new species of plant is considered an invader in the forest.