Costs a gold to play and has the following power.
Tribute and/or evil symbol - > You may pay 1 health. If you do, put a demon token into play.
Does that mean when you play it you can activate it twice? Once for the tribute and once for playing a evil card costing a gold.
1. You play Infernal Gatekeeper. This is an evil card costing gold.
2. At the time you play it, you check to see if any cards in play have the trigger:
3. Infernal Gatekeeper is not yet "in play" - it is "being played" - so its trigger does not activate.
4. Now you've played the card, you start to resolve its text. It has a Tribute ability so you use that.
5. Next time you play a gold Evil card you can use Gatekeeper's alignment trigger.