This is a serious glow up in my opinion. I would still probably kit them out with a few magic items and a way to fly. I would recommend a handful of utility spells, flight, and a contingency. 

My two cents: Fellow DMs, don't forget that your monsters are not limited to their stat blocks for narrative purposes and world building. For example, this lich has Dimension Door and Plane Shift but no normal Teleport or Teleportation Circle. That does not mean yours can't in your world. A lich should probably have a teleportation circle in their lair. Don't be afraid to stretch beyond the stat block when it makes sense for you. Also you don't even have to edit the stat block. You can very safely assume that this creature can create basically any spell scroll in sufficient amounts and cast just about any Arcane spell for the purposes of your story. This block is only balanced for combat and is not the limit of what they can do. It can even be a fun part of the story itself. Maybe the lich is doing something to grant themselves a wish or something like that. And the campaign can be the players racing the lich to obtain the wish and use it against the lich. Anyway, I hope my musings help. Have fun!

Edit: Also, give them a way to cast cloud kill, lol. They have poison immunity for a reason.

Be careful who you call ugly in magic school.

This is a massive buff to the lich, and I think it will be much easier and much more interesting to run these guys. While all the damage and ability changes were warranted and very interesting, I do want to point out how vital it is that the HP was buffed. The previous lich was such a glass cannon that a high level party, especially one with a paladin or cleric that has some way to deal extra damage/debuffs to undead, could wipe the floor with even the most well-prepared lich in just a round or two. Now that the lich has over 300 HP, the lich will be a much more worthy opponent.

Also, getting your soul stolen by a lich is now a mechanical lair feature, so that's awesome and makes the final battle with a lich BBEG very dramatic since players who die can't be revived.

Why does this thing hit for less damage than the Archmage, a CR12???? If you are going to just give spellcasters uber powerful cantrips at least be consistent. He attacks 3 times for 31 damage each so 93 damage total. Archmage hits 4 times for 27 damage each time so 104 damage. This thing is almost 10 CR higher, sure it is double the health but still it seems like this so called ultimate spell caster just got weaker in exchange for more health and damage resistance/immunity. I just want to understand, what exactly is the formula since they no longer give us DM's a guide on how to judge CR. This thing hits for rather pathetic damage when the CR6 mage also makes 3 attacks for 16 damage each. so based on that, the difference between CR6 and CR21 spellcasters just double damage and triple health, but somehow the CR12 spellcaster has more damage and half the health??? what exactly is the math supposed to look like? Yes i know with legendary actions the Lich does more damage, but frankly the fact that a Lich that loses initiative to an Archmage will lose in a fight, or might win with I think 3 HP left, is freaking ridiculous. Legendary actions do not make up for this either, especially since with the range of attacks Drain life might never even get to be used since it is only 20 foot range. The lich also lost the magic resistance ability, which the archmage has. Oh and the super powerful lair actions are gone as well. So yeah, if you want to be an almighty wizard just remember, becoming a Lich somehow means your attacks have less range and you get 1 less attack, and you get some legendary resistance instead of straight magic resistance so hopefully you only have to make 4 saving throws in a day, better off using clone to live forever instead. Oh and they no longer have resistance to Turn Undead, so Clerics have fun making them burn legendary resistance without even needing to use a spell slot, since they don't have magic resistance anymore either Turn Undead as a level 20 cleric is a 50% chance of success roughly. I think I would take the 170 HP of the archmage to not be extra weak to paladins and clerics, not to mention I would usually rather just always have advantage on basically all saves instead of 4 legendary resistances. Just become a legendary Archmage instead, and have your legendary action be casting 1 extra arcane burst like the demilich has, and you will out damage the lich. 

I won't comment on the lack of spells since that is clearly the path they are taking and frankly if you are using a Lich they should probably be entirely custom designed by the DM anyways IMO, but the fact that they went out of their way to change how NPC spellcasters are supposed to function means that I at least want consistency. As it is, I would be more scared of an Archmage with legendary resistances and the Lich's legendary actions than I am of the actual lich. Why does becoming a lich somehow make them weaker? Funny enough the Chain Lightning spell is arguably better damage than the actual attack of the lich, since it could hit for 45 damage against up to 4 people instead of just 31 against 3 people. Sadly its only a once per day, instead of the old lich who could spam the thing because it actually had spell slots and upcast it to hit even more targets potentially. This might be the only spellcaster that got weaker overall compared to the 2014 version, sure it got like triple the health, but it lost in damage by a significant amount, and every other spellcaster got buffed which makes the lich look weaker by comparison.

EDIT: also how does the AC work? because a random magic skeleton having 20 AC is kind of insane, since he is literally better than plate armor even though is DEX is mediocre. Can he cast mage armor on top of it, how about robe of the archmage would that technically work or no? Also he somehow can be killed by a regular non magical dagger now, despite of his magic bones somehow giving him insane AC, so that's kind of odd. Oh but the Demilich does get resistance to all weapons magical or not, so you might also be better off being a demilich instead of a Lich as well. Demilich also gets immunity to psychic damage for no apparent reason, which the actual Lich doesn't have. Demilich is also immune to stun unlike the regular lich. Demilich also has potentially higher damage since it can spam its attack as a legendary action, which for some reason the regular lich cannot and can just inherently fly without needing concentration so over all demilich is probably just more dangerous and more powerful than an actual lich, and the Demilich apparently doesn't need a spirit jar and is just always going to come back to life unless someone can use wish, so unless an enemy wizard or sorcerer has wish the Demilich is fully immortal with no weaknesses depending on party composition.

I just ran about 8 fights between the Archmage and the Lich.

The Lich dominated every single fight with ease. The one time the Archmage did over half the Lich's hp was when the Archmage started first, the Lich messed around and cast lightning bolt and finger of Death (which the Archmage succedded its saves at), and the Archmage crit twice.

Otherwise, the Lich dominated, taking less than 100 damage even when the Archmage got the optimal range and won iniative. The Archmage struggle to overcome the AC of the Lich (it needs 16+ to hit when the Lich casts Shield) while the Lich hit on 10+, leading to the Lich hitting more often, and harder. Misty step and running doesn't help, as the Lich's normal speed plus Deathly Teleport gets it within shooting range. When the Archmage gets outside of hitting distance, the Lich just casts Invisbility and moves closer anyway. If the Archmage cast fly and flew straight up outside of the Lich's range, the Lich would just teleport away, cast invisiblity, and hide. The Archmage might have been able to escape with Teleport, but that was a victory condition for the Lich so no. The Lich can see through Invis with Truesight, so the Archmage couldn't use the same strat.

And, you know, the Archmage got almost all the optimal advantages. 150 starting range and won the initiative between them. Which, is going to be very rare if I didn't make the Archmage go first. Because the Lich has +17 to its initiative, while the Archmage only has +7.

So, tl;dr: Lich has more health, AC, +to hit, Legendary Actions and options that will make the Archmage lose way more often than not.

I will admit defeat the CR21 Legendary creature wins most fights against the CR12 non-legendary creature.... My problem is that it should not come even close to losing any of them. Also it gets rather interesting to me that the biggest difference based on your own post is simply to hit, because the only difference in their to hit bonus is the fact one is arbitrarily CR21 and gets higher PB and for some unexplained reason the Lich also gets 20 AC, while the Archmage AC is straight up wrong at 17 for some reason but I digress. the more interesting thing in this however is the fact that the damage is relative, and only balanced out by the fact that the Lich has higher AC and PB along side Initiative. either way I will still homebrew all Liches I use like I always have, but I really wish we had the chart to understand how CR is calculated in this, because the fact that their damage is relative but they are 10 CR difference in lair is insane to me. My understanding of the way CR worked in 2014 was that even without legendary actions, a creatures CR should not drop by much. So in my original calculations I didn't even bother with legendary actions since in the past it shouldn't have affected it that much, certainly not with a 9 CR difference. With the Lich, his damage without legendary actions is lower than the CR12, which he presumably used to be considering that to become a Lich he was likely an archmage originally.

What’s the point of unlimited Shield casts? Might as well make their AC 25. Also, was there some issue with the word Phylactery that I am missing? Spirit jar just doesn’t have the creativity. 

I noticed that this lich no longer is required to feed souls to it's spirit jar to stop it from becoming a demilich (though the lore states that it can still become one naturally). And even if it did, it's new reigonal effect allows it to do so simply by killing someone - no imprisonment required. This is a lot simpler than gambling on a LVL 9 save or suck spell.

this thing is great, I just wish they didn't change phylactery to "Spirit Jar" it sounded cooler in 5e.

Quote from SharptoothNecromancer >>

this thing is great, I just wish they didn't change phylactery to "Spirit Jar" it sounded cooler in 5e.

I'd seen some complaints in the forums that "phylactery" is a word with religious connotations. Further discussion pointed out that the word also had existed and was used independently, but I'd guess WotC became aware of the point and decided that much like "ki" (which is a concept in active belief systems, even if works of fiction from the same regions as those beliefs have freely used it as a general purpose "magic force") they'd rather shift it to a neutral description.

Quote from theron >>

I will admit defeat the CR21 Legendary creature wins most fights against the CR12 non-legendary creature.... My problem is that it should not come even close to losing any of them. Also it gets rather interesting to me that the biggest difference based on your own post is simply to hit, because the only difference in their to hit bonus is the fact one is arbitrarily CR21 and gets higher PB and for some unexplained reason the Lich also gets 20 AC, while the Archmage AC is straight up wrong at 17 for some reason but I digress. the more interesting thing in this however is the fact that the damage is relative, and only balanced out by the fact that the Lich has higher AC and PB along side Initiative. either way I will still homebrew all Liches I use like I always have, but I really wish we had the chart to understand how CR is calculated in this, because the fact that their damage is relative but they are 10 CR difference in lair is insane to me. My understanding of the way CR worked in 2014 was that even without legendary actions, a creatures CR should not drop by much. So in my original calculations I didn't even bother with legendary actions since in the past it shouldn't have affected it that much, certainly not with a 9 CR difference. With the Lich, his damage without legendary actions is lower than the CR12, which he presumably used to be considering that to become a Lich he was likely an archmage originally.

 I don't know where you ever got the idea that legendary actions don't have a substantial impact on CR. Legendary actions can literally double or triple a monster's damage output. Let's look at what's going on here: you say this monster sucks and is comparable to a CR 12 monster, another commentator generously rebuts that assertion, and now you say that this monster sucks because it shouldn't even be possible for a CR 12 monster to potentially defeat a CR 21 monster (if a monster only rolls 1, it's not going to win) and for lore reasons. These arguments are not in good faith.

Also, proficiency bonus is not arbitrary. Proficiency bonus is decided by CR. What you're lamenting is the fact that challenge rating depends on more than one variable. I haven't touched differential equations in nearly a decade, so I won't even try to explain them here. That said, there's no reason to be put off by differences amongst monsters arising from proficiency bonus. A more dangerous monster will generally have a higher proficiency bonus.

Don't search for reasons to be mad. Just enjoy things.

This simplfied stat block also makes it easier for players who want to become a lich themselves. Just give the player the Spirit Jar trait and change their Creature type to undead.

I have one of these guys in one of the campaigns that I am DMing. He is a lawful good happy little dude. He is a tinkerer who just wants to help out with his various magic items. I named him Blackwing. He forgot everything from his life, but continues to tinker and support the party from the sidelines (he's a pacifist).

Just a friendly reminder to all people out there that just because the stat block says something, don't mean you can't change it to have fun.

I'm confused by the "Protective Magic" reaction. Is the only purpose basically to say the Lich can cast both at will and has no limits on either of these? Is this somehow different and doesn't actually count as a spell so the Lich can cast this on their turn if someone tries to counterspell them (due to the new 2024 rules that only allow one leveled spell using a spell slot per turn? Which I don't think even applies here because the Lich does not have spell slots; it has uses per day). 

Or is it only here because the rest of its spell are technically Actions and thus under the Action section, but since these are reactions, it's listed under the reaction section? That seems the simplest and most direct intent... 

the lich has the choice to either counter attacks or spells with counterspell, I think they did that to make the lich more versatile aand not give it the AC of the tarrasque

It's hilarious to me that they overcorrected so hard, now a standard Lich has more hit points then Vecna. Or, to use a 2024 example, more then a Balor or Adult Red dragon. Yes, something 100% had to be done to make Liches more survivable, but in no reality should the spellcasting human sized skeleton be able to take more of a beating then 20-foot fiendish generals or Armored dragons the size of school busses. It has more hit points then a DRACOLICH...

New Lich is still less tanky than every other monster at CR21. It has the lowest HP and AC within the CR, with the exception of the Solar but they have Bonus Action healing spells so they effectively have around 50 more HP. All the CR 20 monsters in the new Monster Manual also have more HPs than the Lich. Heck, go up by only 1 CR to CR22 and you suddenly have Ancient Dragons with over 400HP. New Lich is like 3 times tankier than the old version but still isn't as tankie as the other monsters in its CR.

Meh. As for all spellcasters, i rather use the 2014 version. Yeah, Lich needed a bit more hp, but their was a way easier response to that: Just fricking use the max hp roll. 198 HP was more than enough, no need to go that overboard. The 2024 thingy of giving everyone tons more hp does not make fight more interesting, just longer, and make player wanna do high damage power build to finish faster rather than using fun and good strats.

Also, no, having a monster with spell slots does not make it more difficult to follow, and bring in something really interesting: upcast. I want my llich to be able to upcast counterspell if deemed necessary... Oh wait, right, the new version of counterspell cant be upcasted, and also is completly useless against a lich cause it will just use a legendary res no matter what... 

I'm not understanding your point regarding the weakness of the Lich in this edition. The new version of counterspell is still effective, and it can be used by the Lich every turn. So, what exactly is the issue? A player whom the Lich counterspells must succeed on a DC 20 Constitution saving throw or lose the spell. That means that the spell will be countered in most instances. I'm also confused when you imply that using counterspell against a Lich is ineffective because the Lich can use a legendary resistance to succeed on its saving throw. That's exactly what legendary resistance is for, and the spell caster just used a reaction to force the Lich to expend a very limited use of legendary resistance (very good trade). You're simultaneously arguing that in the context of counterspell the Lich is both too strong and too weak.

As to your notes about health. Just fyi, the average hit points increase is the result of no longer having certain damage immunities, which required a commensurate change in the stat block to stop the Lich's CR from changing.

Quote from TheOtherRyan >>

I'm not understanding your point regarding the weakness of the Lich in this edition. The new version of counterspell is still effective, and it can be used by the Lich every turn. So, what exactly is the issue? A player whom the Lich counterspells must succeed on a DC 20 Constitution saving throw or lose the spell. That means that the spell will be countered in most instances. I'm also confused when you imply that using counterspell against a Lich is ineffective because the Lich can use a legendary resistance to succeed on its saving throw. That's exactly what legendary resistance is for, and the spell caster just used a reaction to force the Lich to expend a very limited use of legendary resistance (very good trade). You're simultaneously arguing that in the context of counterspell the Lich is both too strong and too weak.

As to your notes about health. Just fyi, the average hit points increase is the result of no longer having certain damage immunities, which required a commensurate change in the stat block to stop the Lich's CR from changing.

The use of counterspell is not something a PC will do at any time just for the fun. Its to stop something really dangerous, as a last ditch countermeasure to stop something really deadly to happen, cause counterspell come with a cost for pc, unlike for this lich who can do it for free. And now, it will not save anything since the liche will just say "Yeah, no." I rarely saw a creature consuming all their 3 legendary res, so now that they have 5, this seems even more unlikely to happen.

I prefear a creature with res and immunity that give it some flavor than a creature with ton of HP who just dont want to die and last 3 more turns of just blasting and making the barbarian useless by constantly paralysing him and denie all the spells of the wizard except if he took resilient.

Did they forget to write the condition for when the Lich's reaction triggers? Other stat blocks with reactions have a triggering condition.