I'm thinking of giving cavalry trained war horses a trample attack as per the Universal Monster Rules in my campaign.
But I can't figure out what the damage should be. Are there examples of Large creatures with trample attacks to go off of?
From the Universal Monster Rules:
"Targets of a trample take an amount of damage equal to the trampling creature's slam damage + 1-1/2 times its Str modifier."
Presumably you would use the warhorse's hoof attack instead of a slam attack. So for a 20 Str heavy horse, that would be 1d6+7.
That works, and I'll rule Spirited Charge double damage applies to Trample Damage.
A cavalry horse was a real monster against infantry. Vs. a charge by a line of cavalry, even hardened infantry would break ranks and flee.
I ran into this same question, except for another creature: the arsinoitherium. Its only attack is a gore attack with its horns. In the bestiary, it specifies the amount of damage from the trample as 2d8+13. But the entry for the druid's animal companion doesn't specify the damage. I guess you would just use the damage from the bestiary? It's the same as the animal companion's gore damage (the large version, at least).
In the absence of a slam attack, I think it should do (gore damage) + 1.5*(Str bonus) = 2d8 + 1.5*(Str bonus).
That's what I was thinking. However, in another thread someone pointed out that since all of the animal companion's attacks do half the damage of the regular bestiary creature, the trample ability could follow that same reasoning. In that case it would do 1d8.
Edit: added link.