Blackwind Lake is located in southeastern Terokkar Forest, in the large mountain valley that also houses Skettis. It is only available to those who have the ability to fly. The lake contains aggressive water elementals that can be farmed for [motes of water].
This area (along with the Lake Ere'Noru and Lake Jorune subzones in Terokkar Forest) is one of the only three bodies of water where you may find Highland Mixed Schools, from which you may catch [Mr. Pinchy].