His spell had simply failed to go off.

Suddenly Zane realized what was the matter: the spell had failed!

The spell of the open mind had failed.

But for some strange reason that he could not fathom, the spell had failed.

Someday, though, I knew that those spells would fail me.

The spell can fail at any moment and must be constantly renewed.

"What will you do if your spell should fail in mid-crossing?"

He had to concentrate on the whole group or the spell failed.

His first spell with the second wagon failed to get it out of the mud.

If I was truly infertile, the spell would have failed, but it did not.