Aberrant creatures will spawn more frequently in the night and while you are in caves. Typically monsters are not limited by “where”, but monsters will always spawn outside of your view, so make sure that the tiles that are out of view are spawn-able (so don’t stand inside a giant mountain range and expect them to spawn). You can see which tiles certain monsters can spawn on here: http://www.unlok.ca/wayward/documentation.html
Another option is to travel to a new world using a Bull Boat to try your luck in some new surroundings. Warning, it can get pretty dangerous as the new monster spawns will factor in your talent when travelling to a new world, so many of the monsters will be harder than just normally starting over.