Ascian influence on Theodoric's reign is only in the most indirect manner: Ascian influence on Garlemald, which itself influenced Theodoric's paranoia and led him further into becoming the King of Ruin. Having Fandaniel be in charge of his body would cheapen the very human terror in that story (plus, would also cheapen Gaius' status by essentially removing his influence from Theodoric mental state).

Also, Theodoric. Grumpy dude with anime hair. Theodric's one of our forum posters.