Backtagging: Yes, please! Seems like I always end up having to anyway... >.>
Threadhopping: Hmm. Let’s take it on a thread-by-thread basis - if you want to hop in, just ask.
Fourthwalling: Not sure how widely known The Last Herald-Mage is, either, but like I said with Dinah - if you’ve actually heard of it, you’re welcome to torment Van by fourthwalling at him.
Offensive subjects : None come to mind atm.
Hugging this character: Oh, sure, go for it. Depending whether he knows your character or not, he'll either stiffen up and push them away or awkwardly hug back.
Kissing this character: What I said for Dinah in this section applies to him too - chaste kisses are perfectly fine, anything overtly sexual is going to make him freak out and retreat into his shell.
Flirting with this character: You're certainly welcome to try; just be aware that he's from a pseudo-medieval canon and won't recognize overtly modern pick-up lines and etc. Also, he's gay, so he'll probably just be horribly awkward at any ladies trying to chat him up.
Badtouching this character: Unless it's coming from someone he's already in a committed relationship with, he won't take it well, so let's just say no?
Relationships/Romance/Sexual with this character: This is actually an angle I’d really like to explore with this particular muse. IC, though, it’d take a loooot of CR and careful build-up before he’d even consider a friends-with-benefits type set-up (because he’s a telepath and empath and ALSO because of serious emotional baggage re: his first real relationship). So as long as you don’t mind committing to a long and careful seduction...
Fighting with this character: He prefers to settle conflicts peacefully if possible, and take a 'live and let live' approach; but if innocent lives are at stake, he'll gladly step up and fight to defend them. As a note: in addition to being a highly skilled swordsman and passable at hand-to-hand, he's the most powerful mage in the kingdom and one of -if not the- highest ranking Heralds (aka Valdemar's answer to military special ops).
Injuring/Killing/Maiming this character: I don't mind him getting injured, physically, emotionally, or psychologically, but here again - I'd like to avoid permanent maiming and / or death.Using telepathy/mind reading abilities on this character: You can try, but he's a telepath and empath himself, so he's got some pretty heavy-duty mental defenses in place just to keep himself sane.
Things That Might Affect Your Muses:
Like I mentioned a couple times above, Vanyel's power set includes telepathy and empathy. But unlike Armand, he doesn't just run around using them on people for the lulz - the Heralds have a very strict set of rules re: appropriate uses for one's Gifts. Vanyel in particular doesn't use his telepathy on people without their express permission (even with other Heralds who're also telepaths, there's a system of telepathic etiquette to follow). So, what that means is, unless your characters give him express permission at some point, he's not going to be reading anybody's minds.
The only exceptions to that rule would be a) in an emergency, and he has no other means of reaching x person, or b) if he were deflecting another telepath trying to snoop around in his head.
The other big thing that might affect other characters is the empathy, which he uses a little more freely, especially since Heralds often have to play detective. If you'd rather not have him use it on your character, though, for whatever reason, drop me a line and I'll make sure not to!
ETA: For a couple examples of what I mean by empathy:
From canon, with some quotes: a situation cropped of where Prince Tashir of Lineas, only survivor and prime suspect in an attack that killed everyone else in the castle, came onto Vanyel after Van brought him into protective custody. He took a read of Tashir's emotional state "and the feel he received was of fear and unhappiness, not attraction. Not in the slightest." . And then, after Tashir reveals that he approached Van to begin with because he's scared of women, and so thinks he must be gay, Van sits him down to talk it out:
"Well, let's really analyze this before we go making assumptions, shall we? Do you know my aunt, Herald Savil? Have you met her formally yet?"
"The o--the lady who was with you?" Now Vanyel picked up only respect, and the good-natured contempt of the young for the old.
"Does she frighten you?" He half-smiled, stiffly. "She should, you know, she's a terrible tyrant!"
Tashir shook his head.
"How about Kylla? She's the baby who's always getting out of the nursery, usually without a stitch on ... Does she bother you?"
Bewilderment. "She's kind of cute. Why should I be afraid of her?"
Vanyel worked his way up and down the age scale of all the women at Forst Reach that he thought the youngster might have seen. Only when he neared women between twenty and Treesa's age did he get any negative responses, and and when he mentioned a particularly pretty fourteen-year-old niece, there was definite interest--and real attraction.
From time to time Vaynel dropped in questions about his feelings toward men; not just himself, but Jervis, Medren, some of the servants the youngster had encountered. And at no time, even as he began to relax, did Tashir evidence any attraction to men in general or to Vanyel in particular--except, perhaps as a protector. Certainly not as a potential lover. Whenever that topic came up, the fear came back.
(Quotes taken from Magic's Promise, pages 192-193)
-The last game I had him in, I mostly played it as a sort-of lie detector (ex: meeting Mother Gothel, he tried to get a read on her only to find out that her gestures/expressed emotions did not remotely match with what he was reading from her, and consequently refused to trust her as far as he could throw her) and to just generally get a read on others' moods (ex: used to grok that something was bothering his apprentice Heather, but had to make an educated guess what that 'something' was).