When applying a spell to a blast rune, do I have to cast it as its own action? Or can I place a spell in the trap as part of the blast rune's initial creation?
The relevant rules are below...
Blast Rune (Sp): As a standard action, you can create a blast rune in any adjacent square. Any creature entering this square takes 1d6 points of damage + 1 point for every two cleric levels you possess. This rune deals either acid, cold, electricity, or fire damage, decided when you create the rune. The rune is invisible and lasts a number of rounds equal to your cleric level or until discharged. You cannot create a blast rune in a square occupied by another creature. This rune counts as a 1st-level spell for the purposes of dispelling. It can be discovered with a DC 26 Perception skill check and disarmed with a DC 26 Disable Device skill check. You can use this ability a number of times per day equal to 3 + your Wisdom modifier.
Spell Rune (Sp): At 8th level, you can attach another spell that you cast to one of your blast runes, causing that spell to affect the creature that triggers the rune, in addition to the damage. This spell must be of at least one level lower than the highest-level cleric spell you can cast and it must target one or more creatures. Regardless of the number of targets the spell can normally affect, it only affects the creature that triggers the rune.
EDIT: To clarify, I think the RAW is very open to interpretation and don't go either way in this case. What follows now is my take on the RAI, not the RAW.
On one hand, since it isn't limited to standard action spells, I feel as though you need to cast it as well (to prevent hour-long casting times to be reduced to a standard action).
On the other hand I can't remember any such spells that target creatures of the top of my head. Maybe some healing spells do, we use those so rarely I don't remember.