Can Imaginem make something feel burning to the touch?
On the one hand, Phantasmal Fire feels "warm" (and no, it's not the Ignem requisite -- that's explicitly just for the light, and Phantasmal Fire explicitly only appears to warm), so it would stand to reason that you could make something feel burning hot.
On the other hand, maybe feeling something burning to the touch is not an "external" sensation, but an "internal" one of pain, in which case it cannot be affected by Imaginem (or can it? HoH:S has some discussion on this on p.63, under "Additional, Minor Senses", but I confess a lot of it is rather unclear to me -- maybe Timothy Ferguson, the author, would care to chime in and comment?).
I also tried scouring through Art & Academe, but to no avail. Any pointers or ideas?
Yes. There is also Illusion of Cool Flames, AM5 p.146, which uses a PeIm Base 2 to destroy the sensation of 'hot' in a burning fire, which would put the sensation of warmth and cold as either part of touch, or as an equivalent (well, or as part of taste, but I think we can discard that one). And that one has no Ignem requisite at all.
Look, cosmology aside (and I need to take cosmology into account when writing for the vanilla setting) no, I'd probably not allow this in a saga where I had both an Ignem and an Imaginem magus.
Frankly, Ignem isn't much of an Art. It does light, and it does heat, and does fire, and that's all. Sure it does bigger attacks, or different shapes of attacks, but I find most combat boring, and throwing different shapes of flame at people is just really dull, IMO. So, taking anything a bit interesting from Ignem and passing it to another Art seems like a bad idea. Particularly Imaginem, which is already a great deal of fun.
Which is to say, in the core setting: sure, you can create the sensation of things being really hot. You are going to have real trouble creating pain, because that's an internal sense so you need high level spells, but sure, high enough to make a person reflexively throw away a sword? Yes. Enough to make their armor seem so hot it hurts? Not so much in most cases because pain is another thing. That being said...if I had an Ignem wizard in my game, no. If I had no Ignem wizard and I had an Imaginem wizard, sure.
Could you elaborate on this a little? No guidelines are given for these "internal senses", except that "Pain, proprioception and balance are treated as mental capabilities with regard to base levels for spellcasting given in the core rulebook." (note that these are Mentem guidelines). They can be affected by Corpus and Mentem, but can they be affected by Imaginem -- and if so, at what base levels? This is not clear from the text, at least to me.
Hmm, I thought that the "reflexively throw away" heat level was the pain level?
Groan, again, I'm confused... "Not so much" means "no, not with Imaginem alone" or "yes, but you need high level Imaginem spells (and how high?)"
And darkness and cold, both can be very useful at times.
Yes. Wont cause physical damage and might need to be rather high level and be aimed at the tactile sense(so if it´s an "illusion" in the sense that it can also be seen or heard, the feeling of hot adds another sense).
OK, I believe Imaginem alone can cause pain, but not by making species shed from an object. You would need the species to appear inside the body, much like water app earing in the body in Lungs of Watery Death, which is not on 5th edition because making stuff appear where you can't sense it is Arcane range in 5th, I believe.
Now IMC a player could convince me that it should be otherwise, but, no in the vanilla setting, you can't cause pain with straight imaginem.