Quote from peteroupc »I assume you discard both Call to the Netherworld and a black creature card at the same time. In this case, in general, Call to the Netherworld will be exiled, its madness ability will trigger (C.R. 702.34a), and the black creature card will be put in your graveyard (C.R. 701.8). When the madness triggered ability resolves, you may cast Call to the Netherworld and you may target that black creature card this way provided that card is in your graveyard (C.R. 702.34a, 601.2c).
Yes, discarded together. Thanks much!