Using the rune in D2:ED gave more experience, more gold and an extra choice of better quality equipment. Specifically, from the
walkthrough:
fight reward: 4500xp, 480g + 1 (1125xp + 3 magical items + 1 other)
rune reward: 6750xp, 720g + 2 (3 legendary items, 1 other)
I tried herding the chicken, as well. Then I got annoyed, and (since I had a recent save) killed it, which was kind of amusing.
Not that Casper dies, but that [spoiler]you get an achievement for it (or at least did in D2:ED)
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