Waou I did not know Szivi had all these artifacts in his hands at the time he got devoured!
The micro management mistake put aside, remains the question of the delicate balance between long term investments (ring of wizardry...) versus immediate power. When a secondary power like you invests so much in powerful artifacts, then temptation is great for the competitor with not so many Rings but many more Swords to intervene without waiting... From that point of view, can't we say the Horror was indeed a manifestation of Justice avenging you for your Greed of arcane power, not taking into consideration more mundane and military power?
OK this is a bit teleological I recognize... still...