Ashling, the Extinguisher

At first glance you say ok-for 4 4/4 and legendary (not that good). However, even though she lacks the evasion ability a closer look into her ability and it made me understand how it pins down opponent aggro-creature decks. Moreover, for a control deck its a pretty solid 4/4. Also, bear in mind that the opponent sacrifices rather than destroy. Opponent is pinned down to block her at all costs to avoid further damage. Could use that to swing by other attacks with smaller creatures (if he choses to block smaller creature he will eat 4 damage). The clock is set on 5 turns with this woman! Plus her 4 defence makes it quite stubborn to remove in a burn deck unlike negator!
I decided to go with her as she is more strategic than first thought.

This creature is very solid in limited play as a 4/4 for 4 mana in black, a color that doesn't often get such efficient creatures. Also, it has a nice ability especially with the abundance of tap abilities and evasion-granting abilities easily available in limited (Aphotic Wisps, for example). Unfortunately, her ability is not so useful in constructed play because of her lack of evasion. Nevertheless, a 4/4 for 4 in black is a good thing, although in Standard any mono-Black deck would prefer Korlash, Heir to Blackblade while a Black-Green Rock deck would prefer Chameleon Colossus in the 4-cost spot. Solid creature, very Limited-playable, not very good in Constructed.