Danzoumaru

One of the four guardians which guard the entrance to the Seireitei. He is the guardian of the Black Ridge Gate (Northern Gate). Sousuke Aizen hypnotized him and the two other guardians so he could use them to give trouble to Ichigo Kurosaki and his friends. However, he was stopped by Jidanbou Ikkanzaka. He is the only other gatekeeper beside Jidanbou to appear in the anime, though it was during the anime-only Bount arc. However, he is quickly dispatched by the Bounts Yoshi and Mabashi.

(Source: Bleach Wikia)