[Dragaera] Yendi and ambition

[Philip Hart]

In the Cycle representation in _Tiassa_ the Yendi are said to represent 
subtlety and misdirection.  It's interesting that while this describes 
Pel accurately, his perhaps most characteristic trait is ambition.

Much to my surprise I've recently been reading some Harry Potter fanfic 
recommended on a philosophy-oriented blog, Crooked Timber.  The first, 
_HP and the Methods of Rationality_, is very interesting intellectually 
but isn't to my mind successful as fiction.  The other, a pair of twin 
novels by Vera Rozalsky, is a much deeper and affecting work than the 
original, especially _Amends_.  In any case, one of the characters says,
'"Snakes travel in a straight line, never mind what they told you in 
school." [...] Yes, if you wanted the straight line drawn for you, ask 
a son or daughter of the House of Ambition...'  IIRC from HP one gets 
the sense that Slytherins are evil and devious, Gryffindors good and 
heroic; both fanfics above suggest that the moral polaritzation we see 
is just historical contingency, that Slytherins are meant to be 
basically Pel but went astray.

So anyway, I can certainly see snakes as devious or evil but I'd never 
thought of ambitious.  Is this a common symbolism?  Or am I just 
overreading a coincidence?