TiwazTyrsfist
Adventurer
I know I'm in the minority here, but I personally really liked Icarnum. I thought it was an interesting system, and it heavily subverted 3.X's magic item economy.
I personally felt it worked well in 3.X
However, that said, I don't think it works in 5e's low item setting. 3.X was built on the concept that you would fill all your slots as quickly as possible, and constantly upgrade them. Incarnum did that. 5e's flavor of (at least in Adv League) by level 10 you may have 4 magic items and 2 of them will be useful, doesn't allow for Incarnum to do anything.
As for Tome of Magic, basically it was 3 takes on "How do we balance moving away from Vancian Fire and Forget Slot Magic without having to completely rewrite the entire game engine?" True naming was an interesting idea that didn't work.
Meanwhile, the fundamental parts of Pact Magic (Gain these buffs as a supernatural ability) and Shadow Magic (Cast spells as a Supernatural Ability no slots) are folded into the Warlock Class.
I could easily see the FLUFF of pact magic being developed into one or more warlock subclasses, both patron and pact type.
Book of Nine Swords was, likewise, an attempt to deal with the fact that, in 3.X, at higher levels weapon based characters were weak compared to casters. The abilities gave fighters advancing power levels to allow them to keep up with Wizards, Clerics, and Druids.
5e has done a lot to fix this power imbalance IMO.
As other's have said, the more mundane maneuvers have been incorporated into the Battle Master subclass, but I would be more than happy to see more maneuvers added in a book like Xanathar.
Additionally, I see no reason that the more mystical maneuvers couldn't be adapted into another subclass. Something in between Battle Master and Eldritch Knight that has access to the Elemental Damage heavy maneuvers.
Also, I really loved the system with the Divine inspired class. I forget the name, but basically my take away was that since your combat skills were divinely inspired, you didn't really have full control of what you could do. It was the one where IIRC you basically wrote your powers on some cards, Shuffled them, and then drew a few each round, and those were the powers you had access to that round. I felt it made combat more interesting because you couldn't just spam the same thing or over plan for the next five rounds.
TLDR:
I loved Incarnum, but 5e is Magic Item Light, so Incarnum doesn't work.
The Two decent parts of Tome of Magic are already rolled into Warlock, though more fluff could be brought in as a new Pact/Patron.
9 Swords is Partially rolled into Battle Master, but I feel the flashier paths could fuel another Subclass with a different feel and be good.
I personally felt it worked well in 3.X
However, that said, I don't think it works in 5e's low item setting. 3.X was built on the concept that you would fill all your slots as quickly as possible, and constantly upgrade them. Incarnum did that. 5e's flavor of (at least in Adv League) by level 10 you may have 4 magic items and 2 of them will be useful, doesn't allow for Incarnum to do anything.
As for Tome of Magic, basically it was 3 takes on "How do we balance moving away from Vancian Fire and Forget Slot Magic without having to completely rewrite the entire game engine?" True naming was an interesting idea that didn't work.
Meanwhile, the fundamental parts of Pact Magic (Gain these buffs as a supernatural ability) and Shadow Magic (Cast spells as a Supernatural Ability no slots) are folded into the Warlock Class.
I could easily see the FLUFF of pact magic being developed into one or more warlock subclasses, both patron and pact type.
Book of Nine Swords was, likewise, an attempt to deal with the fact that, in 3.X, at higher levels weapon based characters were weak compared to casters. The abilities gave fighters advancing power levels to allow them to keep up with Wizards, Clerics, and Druids.
5e has done a lot to fix this power imbalance IMO.
As other's have said, the more mundane maneuvers have been incorporated into the Battle Master subclass, but I would be more than happy to see more maneuvers added in a book like Xanathar.
Additionally, I see no reason that the more mystical maneuvers couldn't be adapted into another subclass. Something in between Battle Master and Eldritch Knight that has access to the Elemental Damage heavy maneuvers.
Also, I really loved the system with the Divine inspired class. I forget the name, but basically my take away was that since your combat skills were divinely inspired, you didn't really have full control of what you could do. It was the one where IIRC you basically wrote your powers on some cards, Shuffled them, and then drew a few each round, and those were the powers you had access to that round. I felt it made combat more interesting because you couldn't just spam the same thing or over plan for the next five rounds.
TLDR:
I loved Incarnum, but 5e is Magic Item Light, so Incarnum doesn't work.
The Two decent parts of Tome of Magic are already rolled into Warlock, though more fluff could be brought in as a new Pact/Patron.
9 Swords is Partially rolled into Battle Master, but I feel the flashier paths could fuel another Subclass with a different feel and be good.