Why does it have to implode every other roll...
Basic CTN is 18, so this roll 'earns' me a snag point... Spell seems to be cast normally but has no effect...
If Ceillen is aware of his fumble, he will try another bolt next round. If he is not, he will consider the creature to be impervious to his attack and will switch to defensive fighting.
BTW, if one astral bolt strikes ever hits a target, it causes 4+wisdom=6 base damage and double (total) damage to any creature or being that is not from the Mortal Planes; including Celestial, Infernal, and Spirit entities. It does no damage to constructs, undead, or other non-living objects or things.