I like it, I really do! However, currently there are only two main uses I see for this - using Ghostmare as a means of anti-deckout, and for use in early game when you have to discard due to not getting enough quanta from a low-pillar start. The first use is kind if meh, imo. For the second use, if you're having such a bad hand, by the time you draw more pillars or other quanta generators, you won't need this - therefore, I suggest the cost be lowered significantly (to 1 or 2 quanta), that way it can be run off the mark in the case of a bad starting hand, and save you the discards.
*re-reads card* oh, it says any discarded card goes to you. Hm, this gives it more stalling use. I see a time life duo being particularly effective with eternity stall, or just with other PC. But still, since only one card can be discarded per turn by both you and the opponent, I still think it's underpowered.
Tl;dr it's UP; lower cost