Barrier Stone (Thaumcraft 6)

The Barrier Stone is a block added by Thaumcraft 6. It prevents all mobs, but not players, from crossing it by replacing air with warding blocks in two spaces above it. It can be disabled by a redstone signal.

When blocking a mob from crossing, it emits purple rune particles. When disabled with redstone, it emits blue rune particles. If a mob would be blocked but a block in the way prevents it from working, it emits red rune particles.