It has AMAZING defenses.110 hp, 105, def, 85 sp def. It also gets defog and you turn, which makes it a great defogger who can pivot. It also gets Roost, reliable healing, and foul play, a move that uses its targets attack for its attack. Also having knock off, it is a very bulky Pokemon that can use defog, has reliable recovery, a pivot move, and two very annoying stab dark moves.
Oh and altho it's monotype, smogon give a good explination here