Gregorius nods.
"I don't want a threat living within our covenant. If we can do that by avoiding the creature being a threat in the first place, or even turning it into an ally, so much the better. If it's going to be a threat regardless, we need to find that out, and either deal with it now, or gather enough information to be able to deal with it in the future."
He'll look to Alcimus to begin closing in on the creature again, paying attention to his Premonitions as he does so.
After a bit more pursuit, Alcimus thinks you're within a few minutes catching up to the creatures. Gregorius has a premonition of danger, but there's little more than that vague sense.
Scott
Keep going, but quietly (unless Fray thinks otherwise).
Alcimus's hackles are now up, and he thinks you're only moments from encountering the beast, in the middle of a dark passage. Anything you else you want to do before pressing forward?
Scott
Is it just a question of "around a corner"?
If so, Gregorius will quietly cast a spell to look round the corner by transfering his sense of sight to a bit of the wall at the corner which he would be able to see down the next corridor from.
[InIm 5 - Base 1 (use one sense at a distance) + 3 Sight + 1 Conc =5. Casting total is (In 6 + Im 2 + Sta 1 + Aura 7 - quiet words only 5 + die 2x4) = 9.5, so should work. I don't think magic resistance should be an issue, as he's detecting issued species.]
[ooc: I've assumed the sight within darkness spell from before we entered the regio are still active] Fray is staying quiet and watching, trying to be alert for the encounter.
[Yes, I've neglected this thread the past few days, partly because I spent all of Wednesday doing an assigment for a potential employer, and all of Thursday driving six hours each way to pick up a repaired car. I'll get caught up on Friday.
Scott]
Suddenly, an enormous shadow darkens the passage in front of the magi and Alcimus. A moment later, a gigantic blur of brown fur fills the passageway, lunging towards the party. As they prepare to meet the charge a disturbing realization dawns on the magi: they're being attacked by a very, very large rabbit--larger than a draft horse, actually. Each magus should roll Per + Awareness against an Ease Factor of 6 to avoid being momentarily stunned by the absurdity, and then tell me what you'e doing; Alcimus, as an animal, acts on instinct, and doesn't hesitate.
Scott
[OOC: Gregorius Per 3 + Aw 2 + die 6 = 11 (invisiblecastle.com/roller/view/4535953/).]
Well, a giant rabbit certainly wasn't what Gregorius was expecting, especially given Alcimus' earlier statement that the thing they were tracking smelt like a predator. So the tunnels are a warren?
He's able to get over his surprise fairly quickly, though - which mostly consists of getting behind Alcimus whilst checking the rabbit and its surroundings for any sign that the rabbit is just an illusion, or is being chased by something else. He also gets a stone ready.
[Second Sight 3 + Per 3 + Aura 7 + die 6 = 19 (invisiblecastle.com/roller/view/4535995/)]
Alcimus, meanwhile, will position himself to Defend Gregorius (as per the rules on page 173). As he doesn't yet know the combat effectiveness of the giant rabbit, he will exert himself (page 173 again) on his defence roll by spending a fatigue level.
[Defense (bite): 11 as standard + 8 from exertion + die 2x10 = 39. (invisiblecastle.com/roller/view/4536001/) I'm going to guess the giant rabbit doesn't hit him here... If relevant, though, his soak is 8.]
If the rabbit does actually attack him (or Fray within reach of him), he'll attack back, but he won't strike the first blow without instructions from Gregorius.
[Attack (bite): 13 + die 9 = 22 (invisiblecastle.com/roller/view/4536004/). Damage is 4 + attack advantage.]
No telling, and rabbits don't normally attack people (or wolves), either. However, it's hard to say what it would be "normal" to expect of a giant rabit in a powerful magic aura. It could be Warped, for example. Alcimus might be able to shed some insight later, when he gets a chance to talk.
It's not an illusion. Also, did you roll the die to avoid surprise?
Yes, it's lunging, at Alcimus because he's the closest target. It turns out that a rabbit's bared front teeth are quite frightening when they're half a foot long. This thing is easily twice the size of Alcimus.
Let's see what Fray is going to do.
Scott
That was at the top of the post:
For the surprise roll: 1d10=3, plus +1 from Per and Awareness, does not reach 6. Fray is momentarily stunned by the absurdity.
At the moment he is unable to gather wits enough to make an action, I assume in the following rounds he may be ok. Let me know how long Fray is staring in disbelief at the rabbit.
[Edit - ooc: how large in terms of size values? +2, +3? It affects spell mags needed to target it directly, so would be handy to know]
OK, the rabbit attempts to bit Alcimus, but misses. Gregorius spends that first round checking for an illusion, while Fray is stunned--but that only lasts for the first round.
Fray judges the rabbit is about the size of draft horse--so about Size +3.
What next?
Scott
Fray will cast a spont effect to try to slow the giant rabbit's movement so we can withdraw. He's not speaking yet, but if it works he'll yell "withdraw".
Casting roll: 1d10=5, so a CT of (35/2), so final CT = 18 vs level 5 effect.
Is that (CT 18 - lvl 5 + Pen 1) a 14 Penetration vs its MR? I'm rusty on Penetration total vs beasts.
EDIT: Should be CT of 17, less 5 for the spell level, plus 1 for Pen. So Pen 13 vs its Might + Aura. I rounded upward initially.
[Penetration against Magical beasts doesn't work any different to penetration against anything else, I think, so yes, Casting total - Spell level + penetration modifiers. Its magic resistance is going to be boosted by the aura, mind, which is going to make penetrating trickier. Also, we should have Aison along as well - do you want to run him?]
Alcimus will exert on his defense again, and then attack the rabbit (was his previous attack successful? He'd have counted "lunging at him" as an attack even if he managed to avoid it)
[Defense: 11 + 8 (exertion) + die 2x7 = 33 (invisiblecastle.com/roller/view/4539519/). Second fatigue level down, but thanks to additional fatigue levels and enduring constitution, his fatigue levels go OK, 0/0, 0/0, -2, -4, Unconcious.
Attack: 13 + die 5 =18 (invisiblecastle.com/roller/view/4539521/).
Damage: 4 + Attack advantage]
Gregorius will send a stone at the rabbit using Invisible Sling of Vilano.
[ReTe 20. Casting total 16 + Aura 7 + die 5 = 28 (invisiblecastle.com/roller/view/4539543/), so no fatigue loss. Spell is aimed rather than needing to penetrate.
Aiming: Per 3 + Finesse 7+1 + die 7 = 18 (invisiblecastle.com/roller/view/4539553/).
Damage: 15 + die 5 = 20 (invisiblecastle.com/roller/view/4539554/)]
That's mostly right, but (assuming he's native to this aura) the aura adds to his MR as well as your Penetration--so it's a wash, and, in that (probable) case, your Pen is effectively 6. (You might want to edit your otherwise excellent blog post on the subject, since it implies that MR doesn't include aura: ironboundtome.wordpress.com/2011 ... rs-magica/).
In any case, the effect doesn't penetrate the rabbit's MR.
Scott
Whoops, missed that attack. Alcimus managed to sink his teeth into the rabbit's cheek and do fairly substantial damage.
The rabbit misses again, and the SG is starting to think Alcimus might be a little overpowered in combat. However, while Alcimus gets his teeth into the lupine again, he does less damage this time.
And here I thought the rabbit was going to be a reasonably challenging opponent. 
It's hurt. Aison's lands his attack as well, making things even worse for the beast.
After receiving the force of Alcimus' bite, the rabbit topples over, falling onto its side. Alcimus needs to make an Int + stress die roll against an Ease Factor of 9. There's not really an applicable ability, because his experience with Size +3 rabbits is rather limited.
Scott
[Int 1 + die 0 (then 2, so no both unless extra botch dice - happy for you to roll them if so invisiblecastle.com/roller/view/4540437/ ) = 1. So, nope.]
I did try to build him for combat (rather than, say, as a lab assistant), although as this is my first Ars Magica combat I was guessing somewhat as to how effective he was going to be. That said, rolling decent exploding dice on the defence rolls will presumably have helped a lot, and he'll be unable to keep pulling off the exertion trick in longer fights or fights without a break (he can basically do it for two more rounds than a normal character).
Ah well. Better that way than the other way round? Especially for a first fight (or at least, the first fight Gregorius hasn't ducked or outright cheated on - I realised the other day that this game has gone the better part of four years without a single attack roll).
Gregorius will ask Alcimus (who alongside failing his intelligence roll is trying to catch his breath):
"Did that smell like the creature you were tracking? I was expecting something less...rabbity."