There were secret spells in elder scrolls the arena if you selected spells in the right order and you might have also had to select the target type touch vs range and so on in the right order

I do not know if it was possible to get any of them to actually do anything other than nothing or crashing the game though

might have crashed the game even before spell purchase

one secret spell might have been named cage

I wonder if it was a bug accessing text from another part of the data file?