I have now played Karthus three times. So I know there is not a TON of experience here to go off. However I got the feeling that he has potential with a few tweaks but is currently slightly underpowered.

I will go over his abilities, commenting on each one.

Q: Lay Waste. An interesting concept with an ability. It is also I think the first time in these type of games I have seen an ability that forces you to use the hotkey. Over all I like the ability I just feel that it needs a slight radius increase. that makes it harder to use for the double damage part of the ability but makes it much easier to use for all other purposes.

W: The wall. The wall seems largely worthless. you find yourself casting it only because it gives you something else to do than spam Q. The enemy team is never afraid to run through it all day. A tiny armor decrease and a negligible speed decrease dont help much due to how short it lasts. By the time the enemy who ran through it is engaged the effect has worn off. I think increasing the duration to 10 seconds so that it lasts a little bit into the fight would be a much welcomed change.

E: The aura. It hits really strong and it drains mana really fast. Situational but it has its uses. I will say that the ability is fine as it is right now. Just situational and draining enough to prevent it from becoming broken.

R: Ultimate. This ability needs major help. 250 damage should be decent for catching a runner. However it is just SO easy to counter. The first problem lies how rarely someone is within its kill range. Currently with the way the game is set up with how small the map is and all the free teleports when someone is low health they are only so for a few seconds. With the casting time added onto the spell you are losing very valuable seconds. This brings on another problem too. That casting time tells people you are about to hit them and gives them 3 seconds to do something about it.

This can be as simple as pressing A/S for a heal that will guaranteed put you out of kill range. Or many of the other abilities that many heros have that are either heals or spell bubbles or immunities. It can even be just go jump in any of the grass that is on the map. The spell doesnt hit "stealthed" targets. So if anyone jumps in one of the many patches of grass on the map they are immune to your ultimate.

I propose the removal of the red beam showing on enemy heros during his cast time.

I would like to know others opinions on the hero and or my ideas. Especially those who have more experience with Karthus.

Take revive and teleport summoner spells.
Team fights:
Wall first(wall is good!), make sure they run through, and then have your teammates rush in.
You rush in with them, turn your AOE spell on so that they are caught in this.
Spam Q correctly. then if they are somehow able to run away, wall again if it's up by then(probably will be, wall the direction they are running towards), otherwise, you always have your ultimate. Remember to keep an eye out on your minimap.
If you somehow die, REMEMBER your 10 second passive, you can still do damage, THEN revive and teleport in to push and/or finish off.
Also Tears of the Goddess.

I'm a newb, so there might be better ways to play him. This works well quite a lot if the other team is not prepared to have a good wall pop up in their running direction(in which case you send your tanks and hitters in first, then follow). Also hope they don't have a good morgana in the other team. If they do, say hello to spell shield a lot.

Q is meant to be hard to use because of how strong it can be if you are very good with it. It also makes him a very high skill cap hero.

His wall is an incredible ability. No offense but your kind of dumb for thinking otherwise. An aoe snare in a team fight is huge, especially one that reduces armor. Stack that with a cryophoenix ulti and an entire team is immobile while you pick them apart. Its also great for ganks, great to save people and makes landing lay waste very very easy.

Defile is very good in design. Very strong ability but comes with a very steep cost.

His ulti is not weak by any means. It kind of sucks this patch because it doesn't do damage with his passive (im not sure if its a bug or not, it wasn't in the patch notes). It did take a nerf in scaling this patch as well but at the end of the game it does 800 damage to an entire team, its a lot of damage.

The change to his ulti not working in his passive castrated him pretty hard this patch, but he is still a strong champion.

I have now spent a few more games both as and against karthus. I am taking back my radius increase statement. I think it was just one of those things where when you play as him it seems really small radius but when you play against him it seems way to large.

The wall i still think needs work. Even watching some other players use him no one ever actively uses the wall.

E is still fine and can be incredibly strong but is still too situational to be too strong.

The ult I want to see it either hit stealth to remove the grass counter. Or remove the giant red beam notifying everyone "IM USING MY ULTIMATE PLEASE COUNTER".

Lich his overpowered, not underpowered. E is not too situational. If you get a tear early enough by 15 minutes in you can use it whenever you need it - just don't use it to farm. Q is enough to farm with.

I'm sorry, but if this is so, they do not know how to play Lich. His wall has so many uses. You can technically use his wall as somewhat of a ward in the jungles to prevent ganks. Just play it down and move on. As long as it's up, you'll see if anyone is trying to gank you. It's very useful and to underestimate it, is what gets most teams killed in a team fight against him.

I agree with YummyCheese, I'm not sure if the ult is supposed to NOT work during his passive. I think it's most likely a bug, but most of the times I've cast it, it hasn't applied correctly to everyone. I don't know what it's about, but I hope they fix it soon. As part of the reason you want to save your ult is so you can use it during your passive 10 seconds to finish off those who are running away.