I've got a player starting tomorrow as a descendant of the Zoroastrian Magoi. He's got Mythic Blood, tied to his Zoroastrian Fire Worshiping roots. He wants some sort of mythic blood power that ties to wisdom, and the natural choice for duration seemed to be "Fire" as Mythic Blood powers are not limited to Hermetic target/range/durations....
I thought it might be cool to have a fire that makes the invisible visible, but I can't quite work out at this late hour the way to construct. The idea being that invisible spirits and ghosts within light of the fire could be seen and perhaps communicated with.
Make the fire necessary, but not an element of the spell in RDT terms:
The duration can be Instant if you only want to REVEAL the target. Make it diameter (+1) if you want them to stay visible for a while.
Method: Recite a prayer in the presence of a fire. At the end of the prayer, the spell triggers (instant duration). Or the spell triggers while you are reciting your 2-minute prayer.
You need a fire, so make it a necessary condition for the spell. Since it is cool, I would give a freebie 5 points to spend on the effect since it has a requisite. YMMV here
Working from blacklinger's suggested base of35.... (Lazy parma: books 4 meters away, and no idea where the guideline is)
-2 mags from the instant duration (or -1 from Diameter) from the Sun duration that he suggests.
-1 mag for requiring a fire (my mad idea)
Range Voice is now the range of the Prayer to the Fire, so it is larger than the fire cracking. But making it the area that the fire illuminates is a cool idea as well.
The Revealing Purity of Fire (CrIm(?)20) R:Voice D:Instant T:Individual. Requisite: fire(-1mag)
A fire that reveals the invisible being in the area it illuminates after you recite a sacred incantation to it sounds really cool.
Level 20 spell. 10 levels of penetration. Fairly low penetration, but hey. We can't do much better It is a cool effect in any case so I would bend the rules to allow it since it is far from game breaking and fits the idea of the player (and is a cool effect to have around). A recently gauntleted magus could make a magic item with "see invisible beings" rather easily, so it is not like it is gonna break your game
Plan B would be the fire to grant the magus the Second Sight ability.
I would go this way. While a fire is burning, the character gets Second Sight with an Ability score of 4 to see anything that could be illuminated by the fire. I'd say that's about Base 15 or so. Let him pick up the rest of the levels in a CrIg effect. It's a Major Hermetic Virtue, giving him a weakened version of a Minor Virtue, plus 50 free experience points in Second Sight, is not at all unreasonable.