The Karthus build for Jungle is Liandry's Anguish and Dark Harvest. This LoL Karthus guide for Jungle at Platinum+ on 13.23 includes runes, items, skill order, and counters.
Karthus Counters
50.6%
(-1.5%)
66.4%
(-3.0%)
2.9%
(-0.1%)
3.2%
(-1.0%)
1,123
(+10)
