So, we fought a powerful illusionist last weekend, and that has me wondering a little about illusions.

1. Illusionary object says what senses it covers, but leaves out tactile/touch, but then follows with a paragraph indicating a person can burn themselves on an illusionary fire. Does it cover touch?
2. If so, what are the ramifications of that? Can I make illusionary stairs and climb them to a higher level? Are the illusions real enough to do that? In the fights this weekend there was some “partial reality” to many of the illusions we fought, but that seems very different (I assume talents, etc) than what is discussed in the standard spells.
3. With illusionary beast, size has no effect on the strength/difficulty of the beast. But is it possible for me to create a huge illusionary dragon and ride it through the sky?

I’m working on the assumption that you can’t do any of these things, but if someone can’t bump into (be physically effected by) illusions, that make them very limited, but if they can we need to have limits to what they can do with them.

Most of what you're saying I agree, that it's not possible. Fire is interesting because it is something you can "touch" but isn't something with any solidity or form. It's all energy. I think that's why the illusion of fire works as your mind will fill in the heat/damage and there's nothing truly physical to interact with. An object (stairs, dragon, glass) will be clearly not there as soon as the attempt to touch it happens.

With a sweep of his hat,

Paul

If an illusion has substance, we're getting into astral projection territory.

So to be immune to an illusionary beast attacking you, you just need to close your eyes so you don't see it attacking you? If there is no reality to it, than things are still very complicated, and if an illusionary object can't withstand touch, it is really more of a cantrip level power, certainly not tier II.

It depends what the Illusion is. An illusion may be nothing more than a trick of light and shadow, but it could (in theory) also be an implanted thought into your brain. For example, Enemy of My Enemy makes you BELIEVE that your ally (or the target) is an enemy, not that they are just wearing a 'enemy suit' of illusion. If you BELIEVE an illusion, it could make you 'feel' it by your brain interpreting the edge of the illusion to be the item, sending signals to you that there is something physically there that isn't. This could even in theory apply to physical damage as Stamina represents you, well, stamina. If you think you're being hit, you're going to dodge out of the way and exhaust yourself because you THINK it is there and act accordingly, even if you are literally fighting thin air in reality. Wounds are theoretically possible, but they would be incidental (ie: you falling against the ground and breaking a rib).

This wouldn't work for things like illusionary steps, as you would need something physical to climb and not just think that you are climbing. This falls into the Creation tradition.

I have personally always been fond of Illusion spells in most RPGs. They represent flexible and strong battlefield control. A useful thing to have up your sleeve. And illusions encourage you as a player to be a sneaky thinker instead of a number cruncher. Of course its always been the case that its easier for GMs to crunch numbers than to adjudicate sneaky thinking, so gamers have pretty much always been debating how to implement Illusions that are neither too awesome nor too lame...

Arcanis has the good fortune of expanding upon previous RPGs and most of its illusion spell seem pretty clear to me, with the most important information embedded in the text of the spell. Waking Nightmare (and Enemy of My Enemy) are "phantasms" that mostly take place in the mind of the unlucky victim. Illusory Beast creates something that is "quasi-real." It helps to fight an IB if you know it is less real than the surroundings ... but you'll still take damage when it hits you.

Illusory Object is not quite as clear, because as Ken points out, the text contradicts itself. I believe that Illusory Object *does* have a tactile component to it. If you create an illusory brick wall then someone who comes along will feel is rough texture. If you create an illusory bonfire then I assume that a character who sticks their hand in it potentially takes damage since it says so in the description. I would guess d4(Primary) in damage is in line with what might be achieved. But as I read the spell that effect is entirely psychosomatic. And I don't think (IMO) that you could ever take a wound from it. I'd give a PC an immediate role to disbelieve as they put their hand in the fire, and once they disbelieve then that Illusory Object has no further power to harm them. Other examples seem to be more thoroughly covered. If you want to try to "run through that wall, which I just know is an illusion even though it seems real" then we're back to the text of the spell which lets you make a Mettle (Perseverance) check.

That's really flexible and powerful, but it's you binding for the scene and it does have limits.

You definitely can't use IO to create a stairway you (or anyone else) can climb. That beyond what you can accomplish with psychosomatic results. Similarly if you get hit with a Force Push, an illusory wall or cage provides no resistance to that forced movement. Illusory Object is not quasi-real.