Not sure you can call it a dump with such a low volume. There's simply no buy support at all, so the price naturally falls. But this is far from being the only coin in this case. Even coins with active dev's like KEY are dumped to oblivion and have no buy support.
Each new month is worse than the previous one since july.
It's probably to all the BTC recent volatility, where the whales are now playing.

halcyon's dev not posting for 1 week doesn't help thought.