Can I suggest some traits?
Paralyzing Fear
When Mummahos (made up name FTW) is in play, all pokémons are locked so they can only switch-out in the end of the turns.
This can be offensively useful for scoring a hit in pokémons before they run. It'll also defensively useful because you can send any pokémon after Mummahos, because Mummahos will take the hit. Very strategic, but maybe broken - can have sideeffects, though.
No effect on ghosts.
Logic: If you see a ghost mummy, you can have 2 reasons. The first one, you get paralyzed of fear.
I don't understand this one, would it make switching low priority or something?
Get Out
When Mummahos is sent in, the opponent's pokémon automaticly returns - like a Roar. It's not broken and can be very useful for breaking setups, batom pass teams etc. etc. Very strategic.
Logic: The second one... you run of fear.
Now THIS would be fun on an entry-hazard using team
Apparition
The opponent pokémon can't attack the turn Mummahos is sent in. Not so strategic but welcome and far from broken.
Logic: read paralyzing fear.
Would be fun ingame and against idiots who use charge-up moves
Elder Curse
Every turn Mummahos is in play, the opponent's pokémon looses life. Pretty basic.
Logic: egypcian curse stuff.
Sounds broken. A tank who hurts the enemy just by being there?
Leach Touch / Death Touch
Every contact attack used by Mummahos acts like a life-draining attack (eg giga drain). Kinda strategic, can be used to make Mummahos the "survivest" wall of all.
Logic: not a vampire but mummies steal lifes too.
Sounds kinda unfair. Imagine if you had this and managed to Focus Punch a Blissey or something. Then again, there's the Shell Bell which heals you based on how much you did, it could be seen like that