spell connected to improvements

[pippin_nl]

Is it possible to change / add a spell so it can only be cast at a certain improvement (Letum Frigus for instance), preferably by editing XML files?

 

[MagisterCultuum]

It is quite possible, but not with only xml. You will need python, but it isn't hard; the code is already used in the Sacrifice spell, which can be cast either in cities with a demons altar or on the Pyre of the Seraphic.

You can just copy and paste that part of the code in the C:\Program Files\Firaxis Games\Sid Meier's Civilization 4\Beyond the Sword\Mods\Fall from Heaven 2 030\Assets\python\entrypoints\CvSpellInterface.py into a new python define in the same file, and set the <PyRequirement> to that define in C:\Program Files\Firaxis Games\Sid Meier's Civilization 4\Beyond the Sword\Mods\Fall from Heaven 2 030\Assets\XML\UnitsCIV4SpellInfos.xml for the xml portion of your new spell. I did this for a few spells in my modmod.