Needing VTT support
1. Relatively grounded with at least a nod toward realism in most systems in play, from combat to resource management to survival.
2. It's dangerous and most of the time even fighting "weak" enemies caries real risk.
3. PC magic is powerful but unreliable and dangerous to use.
4. The game systems are just as worthwhile for non combat stuff as combat stuff.
5. Medieval feel.
A list of the areas where each of the suggested games that I know fail to meet your requirements, and how.
- Realism
- Burning Wheel (BW) is more literary in feel than realistic in feel.
- RuneQuest: defaults to everyone has a little magic
- Dungeon Crawl Classics and other OSR games: the realism only comes from GM inputs, not the rules.
- Warlock - given the rules simplicity, realism is solely via GM input.
- Hero System: system defaults to cinematic levels, but can be tweaked down.
- Rolemaster - The Crits alone kick this out of realism. There are a bunch of realism options, but none remove the insanely frequent & very brutal crits.
- Dangerous - most of the games mentioned so far meet this
- Hero System: Using normal characteristic maxima, very limited non-worn armor, and wielded weapons (rather than powers):
- with 75 point PCs, Combat can be dicey (pun intentional)
- with 50 point PCs, every combat is going to hurt bad.
- OSR - most OSR games will fail to meet this at either mid (5+) or high levels (10+)
- Magic: Powerful && Unreliable && Dangerous to user
- GURPS (Core, DF): It's all skill rolls, no serious risk to caster. A couple sourcebooks offer alternate magic.
- Burning Wheel: Again, magic is mostly skills (unless using Magic Burner)
- Rolemaster: core rules, known spells are automatic - spend the points, it goes off. May require an attack roll.
- RuneQuest: core rules has magic for just about everyone. Make the skill roll and spend the points.
- Most OSR games: magic is tech. Last I checked, DCC included.
- Non-combat mechanics besides magic
- Most OSR games will fail here.
- With the exception of BW, none of the ones I know of those mentioned have robust social conflict systems. Most fall to the reaction roll and maybe a chance to modify it. Most have some rules for use of skills.
- Medieval Feel
- Rolemaster: More fantastic than medieval. No guns in core...
- Burning Wheel: human lifepaths are very late medieval to mid renaissance. Weapons lists include renaissance level firearms.
- RuneQuest - the rules presumption is bronze age.
- Warhammer FRP (all editions): firmly Renaissance tech, and decent firearms.
- Zweihänder: is to Warhammer FRP as Pathfinder 1E is to D&D 3.5; the tone and setting are equally as renaissance.
- Hero can do medieval feel, but isn't great at it. It can do a pseudo-medieval quite well.
- Ars Magica - while medieval in setting, the GM needs to actually enforce that...
- Warlock - It's a bit less firmly Renaissance than WFRP (Its clearest influence). The lack of any mechanical differentation of demi-humans can be help or hindrance on the feel.
Ones mentioned I don't know enough to add in above, and what I know:
- Mythras - I know it's Mongoose RuneQuest adapted to be more like classic RQ, but I've not gone deep enough to know how adapted it is.
- Since I mentioned MRQ, Legend (by Mongoose) is just Mongoose RQ with the overt Glorantha references removed.
- Hârnmaster - Core is very medieval. Skill system is broad, but shallow - I don't know it well enough to judge. I don't know the magic system at all.
- Unicorn Hunter - this thread is the first time I've heard of it.
- Savage Worlds: cinematic/pulp tone. I don't have their fantasy companion.
I'd suggest that Warhammer 1E or 4E is probably the closest fit...
But Hârnmaster, GURPS, or BRP/RQ may work just as well.
Getting the optional rules right, RM can get where you appear to want, but it's got the mathiness issue. Hero likewise.
I once ran CORPS 2E (now sold in PDF as "CORPS v1") (by BTRC) as a fantasy game. It's very realism focused, rules on the lighter end of medium, reduced dice mechanics and a build your own powers magic/powers system. Combat is not only deadly, but non-magic healing is suitably slow... It was brutal. Lots of fun, but combat was deadly.
When you add robust VTT support, several of the survivors fail.
Still, looking at the field, I'd suggest...
- BW - it's easier to just say no to the renaissance elements.
- Against the Dark Master- it is streamlined from MERP, which was itself streamlined from Rolemaster, but definitely retains the parts of MERP I liked.
- CORPS v1 - (if in a toolkit mode) The core works quite well...
- Savage Worlds (based upon the recommendations of it I've seen, and my own read, but not play/run)