Hulzarrian carp

 came from the planet Hulzarr Prime.

They secreted a nerve toxin that was deadly to most mammalian life forms. Bev Tarrant hoped to use the toxin against the Fifth Axis. Irving Braxiatel poisoned himself and Mushtaq Anson with the toxin, but they were given the antidote in time. (PROSE: Five Dimensional Thinking)