I've probably seen them but can't recall them. I had forgotten that the rune priest was in 4e until I was flipping through one of the books. Would be one to look at though for ideas. I find a lot of the 4e paragon paths and 3e prestige classes are good inspiration for subclasses. Maybe I should go back and have a look at water themed divine classes for my clerical ocean domain.
The Covenent Agent was cool because it came with a couple feats to make the assassin/avenger build work during heroic, and then the Paragon Path was just super fun to play, and really synergies what the two classes had in common.
A 5e version would focus on being inescapable (distinct from simple mobility), and centering your attention entirely on a single target until they are dead.
So, I’d give it a Mark or Shroud or whatever, let the Agent get Sneak Attack on their Shroud target no matter what, and layer in spells that can only be used against a target with your Shroud on it, like a teleport that must bring you closer to them/bonus action to teleport next to them within X feet, hold person, ensaring strike or something like it, wrathful Smite, etc.
Maybe rather than it being only doable against the Shroud target, the Shroud enhances these effects?
I’d also go ahead and give them a channel divinity power at level 9.
Depends on what the purpose of redoing Tome of Battle is.
If you're looking to cover the archetypal flavors of the ToB classes, that's definitely doable within the fighter and monk. Arguably some of them are already covered by existing fighter and monk subclasses.
But if you're looking to resurrect the idea of an in-depth resource and maneuver system for martial characters, you should probably do that with classes built from the ground up for it. The problem with trying to do it within, say, the fighter class is that the fighter only has a fraction of its power budget allocated to its subclass features. Look at the difference between eldritch knight spellcasting and full spellcasting.
I'm a diehard fan of incarnum magic's mechanics, but I'm kind of indifferent to the flavor. So when I started thinking about how to bring those mechanics into 5E, I decided that incarnum users were basically monks: essentia as your qi, it just makes sense. However, it would have been rough trying to cram a whole incarnum system into a monk subclass, and the end result would probably be unsatisfying. Gotta build a whole new class around it, even if that class's name is just "Monk 2.0".
How complex and multifaceted are the incarnum rules? Why couldn’t a subclass just use ki in a new way?
I'm not threadcrapping, or suggesting that we don't need more archetypes, just that some of the stuff I've seen in this thread can be handled pretty well with a combo of MC and background and/or some easy and harmless reskinning. I also wasn't actually suggesting the trickery domain there specifically either. Something more damage focussed would probably be a better fit, and, really, the answer could well be to go Rogue/Paladin. Even the gloomstalker is a solid base for an aspected assassin depending on your tastes, as is the shadow monk.
If we wanted a Holy Assassin, what would you suggest? A Rogue with some spells, a cleric with some assassin? Something else entirely? Just curious.
See above for one very rough draft. Another way to go might be to get weird, and give the rogue stuff no divine class has, like unarmored defense, the ability to track your Marked target even when it would normally be impossible, maybe even see them when they’re invisible, and like, a soft damage boost in the form of 4e executioner’s Lethal feature. Ie, when you reduce a target to X HP or fewer, you can instead reduce them to 0.
Either way, I’d also add in the ability to make your SA damage Radiant or Necrotic.
Another assassin ability that a rogue could easily have would be more ways to get Reaction attacks against a chosen target. They make an attack while within reach of a weapon you are holding, attack them as a Reaction (with advantage if their attack misses). “At X level, you can do this while using Uncanny Dodge” would be sick as hell, even if it had to be a high level feature.
They move willingly while within 30 feet of you, teleport or dash or whatever and attack them.
Etc.
