Cheapest priced copy (Rivals of Ixalan): $0.69 at Card Kingdom, near mint, their price list as of .
Siegehorn Ceratops 
Creature — Dinosaur · 2/2 · Rare · Rivals of Ixalan Promos · #171p
Enrage — Whenever this creature is dealt damage, put two +1/+1 counters on it. (It must survive the damage to get the counters.)
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.69 to $7.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Rivals of Ixalan Promos | 171p | Rare | $1.99 | $7.99 |
| Rivals of Ixalan Promos | 171s | Rare | — | $2.49 |
| Rivals of Ixalan | 171 | Rare | $0.69 | $1.99 |
2 rulings from Wizards of the Coast
- 19 January 2018If multiple sources deal damage to a creature with an enrage ability at the same time, most likely because multiple creatures blocked that creature, the enrage ability triggers only once.
- 19 January 2018If lethal damage is dealt to a creature with an enrage ability, that ability triggers. The creature with that enrage ability leaves the battlefield before that ability resolves, so it won’t be affected by the resolving ability.