hm *g
only problem perhaps :
i have read that you can only have 3 random events / turn i another thread here on the forum .
if random events are set common and if you have 15-20 provinces you get almost every round 3 random events. so there will be 4 and the player knows that someone cast it on him . then he just has to check the pathcosts of the ritual and look at the other players which ones national mages could have these path . most likely you have to do more important things to do with your pretender .
so for the first 20 or so turns his guess who has most likely done it can be made with a probability of at least 70-80% i guess
later when path increasing items are forged and independent mages are found it can be almost everyone though .
if one has taken luck 3 and gets these bad spells cast on him by you quite often he will get suspicious too .
i would try to do it not on my neighbors but the farer away players
i think they will believe that one of their neighbors did this to them
just hope that your scout doesn't get discovered or get the info which is the capitol / richest province of the target in another way
many of them are quite expensive or have high requirements :
tidal wave e.g. kills 40% of population this is excellent . but it is evocation 9 and needs water 5 +15 gems so it is for lategame.
but which one i find really nice at the moment is blight
alteration 4 so you get it quite quick
2E 1D are the requirements and 5 earth gems .
a machaka black sorcerer can cast it .
the impact you get from the 5 gems is nice :
-40 gold for the target
- 5% poploss
- 15 points unrest according to sunrays library
so your target normally has either to reduce the tax for 1 turn to about 50% to get back to 0 unrest or loose around 10-20% of his taxincome in this province every turn the unrest doesn't get reduced
but i think an arrow from the sky which most probably kills a standard unproteced mage is better than the population killing unrest increasing spells .