Spikes are a block used for home defense, added by the Blastcraft mod. There are three varieties: regular, flammable, and poisoned. If a player or mob lands on the spikes they take damage. Note: I was unable to set Flammable Spikes on fire using a Flint and Steel.
ICBM introduces Poison Powder and it's made by adding a Fermented Spider Eye and a Rotten Flesh.