So, I wanted some more eyes on this for some fun ideas. I have this big, half-red-dragon warlord named Zenkath as the effective BBEG for my sunday campaign. After the two players beat one of my other bosses (note to self, wizard against fighter equals wizard gets big owies, no matter the level difference), I decided to play it a little, for lack of a better word at this time, meaner with Zenkath, as he's supposed to be the evil faction's big boss. Some context, as the kind of adopted son of a legendary red dragon in my setting named Za' Chien, I figured he'd have access to basically any magic item a martial could as for, via the hoard as well as his various conquests. I already gave him a +3 adamantine plate to help him tank more damage (I made it adamantine because I was feeling evil), as well as a belt of storm giant strength and a unique, large-creature-sized, 4d6 fire damage version of the flametongue greatsword (which also acts as a +3 weapon btw), so he's already pretty stacked, as I figured a BBEG should be. I'm coming to the forums to ask if any other Dungeon Masters have some ideas as to what items he should also be utilizing. I've been tuning him all day to give the players a challenging fight at later levels, so I want something that'll make them fear this guy, especially after the previous boss was a dud. In particular, since he's got one attunement slot remaining, if he was a player, I'm wondering what would be good for that slot (the evil side of my brain is leaning towards an animated shield). Basically, refer to title, and go nuts! Let's get evil with this guy.

Honestly, what he probably needs more than items is minions. The many PCs on one enemy dogpile usually goes unsatisfactorily, because the enemy only gets one turn. Even with legendary actions, it's hard to make it work. A couple of casters in support and some royal guard would do him a world of good.

Also, any items you give him are going to be the players' afterward. If this is end of game, that's fine, but otherwise you're going to have PCs running around with insanely powerful items. (You can avoid this by giving him powers instead.)

minions you say?

buffed bag of tricks

any figurine of wondrous power you want (do the t-rex one!)

*gasp* YOUKNOWWHATWOULDBE SICK? putting a bunch of enchantments on that +3 flame tounge. I'm talking defender(make him impossible to hit), sword of sharpness, NINE LIVES STEALER, fizban's has specical draconic weapons, Sword or the Paruns(gmgr), vorpal sword, some kind of AOE flamethrower effect, possibilities infinte

Quote from jl8e >>

Honestly, what he probably needs more than items is minions. The many PCs on one enemy dogpile usually goes unsatisfactorily, because the enemy only gets one turn. Even with legendary actions, it's hard to make it work. A couple of casters in support and some royal guard would do him a world of good.

Also, any items you give him are going to be the players' afterward. If this is end of game, that's fine, but otherwise you're going to have PCs running around with insanely powerful items. (You can avoid this by giving him powers instead.)

 All very true. I made the mistake of giving my mini-boss that was supposed to eliminate the party a couple... lets say overpowered items and leave it at that. Anyway after they, mostly with the help of their army of NPCs, defeated the mini-boss, they got the items. Now I got a Dragonborn paladin who can breath weapon twice and do it as a bonus action. As well as a few other interesting power-ups. So yeah... moral of the story: don't overpower your boss with items. However giving them special abilities and powers, whole nother story. One which doesn't have a moral. EDIT: I just saw the last sentence of ji8e's comment. 

Quote from IMPLAYS >>

Quote from jl8e >>

Honestly, what he probably needs more than items is minions. The many PCs on one enemy dogpile usually goes unsatisfactorily, because the enemy only gets one turn. Even with legendary actions, it's hard to make it work. A couple of casters in support and some royal guard would do him a world of good.

Also, any items you give him are going to be the players' afterward. If this is end of game, that's fine, but otherwise you're going to have PCs running around with insanely powerful items. (You can avoid this by giving him powers instead.)

 All very true. I made the mistake of giving my mini-boss that was supposed to eliminate the party a couple... lets say overpowered items and leave it at that. Anyway after they, mostly with the help of their army of NPCs, defeated the mini-boss, they got the items. Now I got a Dragonborn paladin who can breath weapon twice and do it as a bonus action. As well as a few other interesting power-ups. So yeah... moral of the story: don't overpower your boss with items. However giving them special abilities and powers, whole nother story. One which doesn't have a moral. EDIT: I just saw the last sentence of ji8e's comment. 

 Also, if you do give your players overpowered items, there's nothing wrong with going to your players and saying "Hey, I know those things I gave you are hella fun, but they're making it hard for me to balance encounters, and they're letting the players who have them dominate the game too much, so I want to tone them down to make things more fun for everybody." Assuming your players are reasonable people, this will probably work.

(You could also unilaterally depower the items, but that's much more likely to create problems in your group.)

A warlord in D&D should also have some means of flight, and something that gives Adv on saves against spells (I think there is a cape or cloak that does this).

But more important, he also should have a personal entourage of elite guards.

I should have specified this earlier, but yes, this guy is intended to be an endgame boss.

Quote from Agilemind >>

A warlord in D&D should also have some means of flight, and something that gives Adv on saves against spells (I think there is a cape or cloak that does this).

But more important, he also should have a personal entourage of elite guards.

 Honestly, I’m considering this, but I’m wondering if it would be more in character for him to not have guards during the fight. Still, I’ll toy around with the idea of having an honor guard.

Quote from Agilemind >>

A warlord in D&D should also have some means of flight, and something that gives Adv on saves against spells (I think there is a cape or cloak that does this).

 mantle of spell resitance. you could combine it with wings of flying for the flight aspect

If you want to be dramatically unfair there is always the vorpal sword which on fighter can get a >50% chance per round to instantly kill a player but I don't recommend being that mean. 

As a more serious suggestion

• The eversmoking bottle is fire themed and plays to a half dragons strengths.  A half dragon has blind sight so it less effected by things that block vision like smoke. You can also easily justify making that effect stronger by giving them an item like the Red Dragon Mask which grants additional blind sight for 5 minutes. Though this may be a version bestowed by the half dragons parent in order to imbue them with more draconic power ( aka only works for a red half dragon of their lineage)  as opposed to being a legendary artifact of tiamat.  
• Another option is the cube of force it lets them create a barrier that blocks spells meaning that casters will need to enter melee range to attack them.

Something I also do personally to help dragons stand up against casters is let them expend their breath weapon as a counter spell or dispel magic. It's kind of like the beam clash you will see in allot of games. Either dragon uses a reaction to spend it's breath  to negate the spell without doing damage or if their are immobilized on their turn they explode in a fireball of their element ending the effect as an action.   The caster gets to use up a powerful attack and the dragon gets to keep fighting.  I prefer it to relying on a large number of legendary resistances. 

Finally, you don't actually have to follow player rules for a boss. I would focus on making a fight mechanically interesting as opposed to following player rule likes attunement. The players probably won't notice you breaking them any way. 

I don't know if it's been said, but it kinda sounds like you're using the character creation feature to make enemies - if that's the case, you shouldn't do that. PC's and monsters are balanced differently for different things. A BBEG that was built as a character will almost always go down fast; they're generally glass cannons compared to the monster stat blocks. 

I'm considering giving him condition immunities like his draconic father has to try and prevent the players from just cheesing the fight.

Iron Bands of Binding. My favorite magic item