I would have to say, the new type would be called "Shabby". It can withstand pollution, but a rather weak type.
Make a type that is immune to Ghost, is Super Effective against Ghost and Fairy, as well as any unspecified attribute such as weak against this and that...
I'll take up that offer. I introduce the
Soulless type! Ghosts can not find a soul in this type to possess, therefore making Soulless immune, and since that is the Ghost's only strong point, the Soulless easily dominates the Ghost. Since this new type has no soul, there is nothing that the Soulless would ever desire or wish for, therefore having no love for fairies. As a result, the Soulless, thinking these fairies a waste of space, goes to extreme measures to effectively exterminate all Fairy-types. However, these Soulless have no real defense against psychic manipulation, and the Fighting-types naturally have more bulk than the Soulless, which is all that the Soulless use.
Alright, think, think, think....
Got it! Make a type that is super effective against Fire, Water, Grass, and Normal, is immune to Ghost, Dark, and Psychic types, has a weakness to Dragon and Fairy, and is not effective against everything besides the types that it is super effective against and Fighting, Steel, Rock, and Ground, to which it is normally effective.
To sum up:
Super effective against: Fire, Water, Grass, Normal
Normally effective against: Fighting, Steel, Rock, Ground
Not effective against: Flying, Poison, Bug, Electric, Ice
Immune to: Ghost, Dark, Psychic
Normally affected by: Normal, Fighting, Flying, Poison, Ground, Rock, Bug, Steel, Fire, Water, Grass, Electric, Ice
Weak against: Dragon, Fairy
Yes, I am VERY specific about type matchups.