With Karthus gone,there will be 5 champions left that still have a non static ult mana cost over 100
So on PBE Karthus is getting his ult mana cost reduced from 150/175/200 to a static 100 mana cost at all ranks, which will bring him in line with what about 95% of the champion roaster that has a mana cost on their ult. (Note that I do not count low CD ults like Corki or Zoe have, or stacking ults like Kog'maw and Kassadin have, those don't have a 100 mana cost for a different reason.) Now beside Karthus, this are the 5 champions left that still have their ults mana cost either over 100 or grow over 100 (you will notice they are all rather old champions):
Zilean (125/150/175),
Amumu (100/150/200),
Zyra (100/120/140)
Vi (100/125/150), and the odd
Twisted Fate (150/125/100).
Riot has been bringing champions ult costs in line over time either through reworks or direct cost changes like Karthus got and with this post I hope that they will bring in line the last champions that still follow these old balancing rules (beside maybe TF which might have that mana cost for a different reason).
If I missed someone, please tell me and I will add it in the post. I did try to look through all the champions costs, but I might've still miss someone.
Also fun fact, last time a champion got his ult cost directly changed to 100 (at least that I remember) was in patch 5.5(Bard release) to
and had the following quote "For a while we've been normalizing mana costs on ultimates, and Sona's the recipient of the next round. Sona buffs. What a time to be alive."
Tormented Soil have a mana cost above 100.
In general I feel like mana costs have way too little impact on the game, especially for newer champs.
ult for 1 second plus initial cost is about 115-135