I've been a big fan of Aqua Dragons "Diamond Tank Karthus" back in the day. It was effecive because Karthus' base damage was very high, you could build no AP items and consistently do the most damage in the game.

This is no longer the case, Karthus' base damage has been nerfed to the ground over the last few years. Aqua Dragon has practically fled the League scene after dropping to Platinum. Needless to say, It's time we take Tank Karthus back to the drawing board.

My solution?: Heal Tank Karthus

https://op.gg/lol/summoners/eune/DaddyMaterial-Meow

(Filter my games by Karthus, and scroll, not EVERY game is tank karthus.)

Rather than relying on pure health and defenses, we're build AP tank/sustain items to use Karthus' as a very effective healing tank and damage dealer. Comparable to a Swain.

Karthus is MANA HUNGRY, Rod of Ages will convert that mana to health. Karthus stacks conquerer like no other champion, more healing. Karthus deals DAMAGE, Riftmaker will convert that to health with omnivamp. Revatalise will increase this healing and Karthus' quickly becomes very tanky.

Karthus' biggest weakness is he's squishy and vunerable. You get invaded and punished very hard early, this build gives you the dueling potential to hold your ground, have impact around the map and contest objectives very early while also scaling into a powerful late game burn mage.

Really think of yourself as a Swain. You are a tanky battlemage. You can frontline fights while doing a LOT of damage. You don't want to die freely to ult on this build, you want to survive and have pressure in the fight while zoning and helping your team.

Pros:
Dueling potential, you are no longer 1 shot. RoA has a really nice build path and you stack conquerer very effectively... from your first base you will out-duel most of your jungle opponents and perform very well in 1v1s, 2v2s and 3v3s.

Impact around the map, Karthus' is a chronic full clearer but with this build not so much. You can hold your ground against invades, and even invade yourself. You have the ability to contest objectives much earlier than an AP Karthus would... we aren't relying on raw AP scaling with this build, it's much more powerful early-mid game than usual Karthus

You have a very nice late game, You aren't running in and dying anymore. You're going to survive much longer. Your liandrys will do 10-20k+ damage every game with this build. It's very supportive, you can basically frontline and still deal the most damage, your E is like a constant Swain ult.

Cons:
Ult is meh, it's not bad but we're sacrificing a lot of ult damage for our survivability. Ult relies on RAW AP and we're mainly building items for their passives, thus sacrificing such. I really think it's a worthy trade off.

Clear does suffer, usual Karthus can clear 10+ cs per minute... this is because of BFT. We don't build BFT but you can still achieve 7+ cs per minute which is more than most junglers.

Early Game:
This build comes online the minute you buy catalyst, Karthus burns so much mana and Catalyst will heal you 20 per tick. Full clearing over and over is a waste, do it if nothing is happening but don't be scared to contest, invade or gank. Try to keep 7 cs per minute while doing as much around the map as you can

Mid game:
This is your strongest point, once you are finishing Liandry's and Riftmaker. Shadow your teammates and really try to do as much around the map as you can. You are much more able to frontline and be the initiator in fights with this build, take advantage of that. This is where you want to try to get all objectives and help your team make progress around the map.

Late game:
You're an incredibly high damage battle mage. Continue to position well, Don't run in and freely give your HP as a FULL TANK would, you want to play as if you were a Ryze or Swain, be at the frontline of the fight but your main job is to apply liandrys burn and deal damage. Unlike normal Karthus' builds, your power isn't in your passive or ult. It's in your Q and E, so survive for as long as possible while chunking the enemy. You scale extremely well so continue to contest and be aggressive.

Jungle - I'm a jungle main, Karthus in the jungle suffers hard from invades and being unable to have impact early. I think this build is a very nice solution, I can defend myself and invade much better than a full AP Karthus. You clear faster than most junglers still.

Mid - This build is EXCELLENT into melees, your E stacks conquerer so well and you will simply stat check most melees once you buy catalyst if you can stick to them with your E. Rod of Ages is so nice to lane with, you will sustain match ups such as Syndra or Xerath while also outscaling them. I would recommend roaming a lot more, your wave clear is excellent and you aren't vunerable around the map as a standard Karthus would be.

ADC - It's alright, I think Dark Harvest full AP Karthus bot is really strong and I don't think this build is weak botlane, just ADC DH Karthus is really strong. Our build is optimised to roles were Karthus has to survive and have impact, on botlane that power doesn't really excel.

Top - It works but the match ups are slightly harder, you can't really roam and it's just worse in general (having to take TP, being unable to roam, much tankier opponents).

Support - Karthus has no lock down or supportive abilities, it's just alright. You can play it like any other mage support.

Rod of Ages - Really nice sustain, you will heal 10k+ or more in each game. Catalyst makes it such a nice build path, the moment you get Catalyst you come online and have much more power than a Karthus' who builds lost chapter first.

Liandry's - Late game burn is unbelievable. Liandry's burn becomes more significant than BFT's around the 1200 health mark, this means late game your burn will melt your enemies so much faster than BFT could. You survive longer, and thus can apply this burn for longer too, It's tank Karthus' main threat. You can deal 30k+ damage a game with Liandry's alone into the right comp.

Riftmaker - The omnivamp is worth it. Karthus deals DAMAGE and riftmaker's omnivamp will turn that into so much sustain. You will get 100+ AP from this item since we're building a lot of max health. You CAN go shadowflame if you want to deal more damage but the tankines from this item is very good

Together Liandrys and Riftmaker will give you +12% damage in fights from the guise passive.

Conquerer - Karthus stacks it very effectively, and from level 1 it's a really powerful rune. +20-30 AP in early levels is enough to make your ganks much more effective. Late game with deathcap this will give you around +60 AP and a LOT of sustain in fights. Dark Harvest or First Strike just don't match the early, mid or late game of this rune on Tank Karthus

Revitalise - Our build works off of sustain, this will give you a lot more health power and thus does a lot of work. This build isn't reliant on ult, so axiom arcanist or ultimate hunter are just less significant.

Building armor/MR on Karthus before worked because his base damage was so incredibly high. In the last few years Karthus botlane had risen to consistently be 55-60+% winrate in high elo. Riot responded by nerfing Karthus' base damage multiple times, and around a year ago when BFT was introduced Karthus jungle become broken so they nerfed his base damage again, which IMO fully killed the full Tank Karthus build.

Karthus' base damage is very low now. He is reliant on AP to stay relevant and scale. Sunfire Aegis or Hollow Radiance are complete *** cheeks because they don't make you much more tanky, and you do significantly less damage than Liandry's + Riftmaker. If you build Unending Despair you have worse healing than RoA + Riftmaker. Frozen Heart gives mana, but no damage and no sustain.

No matter what, the numbers are just in favour of AP tank Karthus now, and full tank karthus is completely inviable.

(Zhonyas is ok !)

If you are unsure about anything, please feel free to watch my replays.

https://op.gg/lol/summoners/eune/DaddyMaterial-Meow