Gengar's Purpose (other than to troll people, being dead and all):

SubDisable? Sure, why not? You say that Gliscor poses a problem to my team? Well, think again. Gliscor is nothing when he can't use Protect to get some 12% recover from toxic heal, and without that, Gliscor is not only prey to a mighty strong Shadow Ball, but he has either spam Substitute, which will make it lose 13% damage each turn, or it can try to fend for itself with Ice Fang, in which Shadow Ball will easily result in a 2HKO. Not only that, but this guy renders Chansey/Blissey TOTALLY useless. If given the chance to Disable their Wish, then spamming Focus Blast wont be such a bad idea. Disable is possibly the best move on this set, as it makes Choiced pokemons have to either switch (and let me get up another Sub) or forced to stay in and use Struggle, which  would make them lose 25% of their HP, and no damage to Gengar, since it is immune to Normal type attacks. So the mightiest of the trolls begins to take his throne and crown.