In the Jade Regent campaign, a ninja is sent to kill the PCs… but at level 18~20 when the ninja attacks the PCs it’s almost irrelevant as each time he kills a PC they just resurrect. They have plenty of money to resurrect and even though I use the system shock type house rule (every time you res you must make a DC 20 CON saving throw or lose 1 CON) my PCs saw the ninja as an annoyance, not a real threat. I figured, in a world with epic-level PCs and an epic level ninja, assassins would have ways to circumvent the endless resurrection. I came up with this – ghost poison – which didn’t kill my PCs but aged 3 of them into their 60s and 1 into his 70s. They took the ninja seriously after that and actively hunted him down. Shared here for other high-level ninjas and assassins out there.
Itachi will now use ageing poison – distilled from the tears of a ghost – to kill the PCs as they have too easy access to raise dead magic (and the funds to pay for it). When he hits with a death attack the target must make a DC 25 Wisdom saving throw or age 1d4 x 10 years (or half as much on a success). For every 20 years aged this way, the target takes a permanent -1 on all physical attributes. When the target reaches 60 years old they take a permanent -1 on all attributes and must make a DC 25 Constitution saving throw each time they are exposed to the poison or die of old age. The target automatically dies at the age of 100.
If the PCs do not have an age listed on their character sheet assume they are 20 years old.