"Never give a ride to a demon hitch-hiker."
Or
"Never ride with demons."
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"Never fall asleep with a full bag of gold, while in the company of a dwarf."
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"Be wary of skyclad women who cunningly never let their feet touch the ground."
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As I have written these, I suddenly realise that the last four I wrote sound more like good advice and common sence than Geas.
It's not like I used to wrting these things.