[Tuidjy]

Even historians cannot agree on whether horses have ever been trained to do this.
I am sure it can be done, but I do not see the point. Charging pikes from the
front is suicidal and probably inneffective. Going through the trouble and
taking the time to train a horse so that it is more afraid of its rider than from
a wall of spikes will result into a very expensive horse that is likely
unstable, twitchy, and not good for much but charging into pikes. Once.

Lets not confuse charging into a wall of pikes and a wall of thrusting spears.
A cavalry lance is a quite a bit shorter than the former, but significantly
longer than the latter. The horse may shy from the spears as well, but the
spearman would be a lot more likely to run much earlier.

Back to Dominions. In the perfect world, this could be modeled as combination
of defense and repelling damage. But I think that the effort necessary for
getting it right would be better spent elsewhere.