Undercity Troll

Renown is a triggered ability. “Renown N” means “When this creature deals combat damage to a player, if it isn’t renowned, put N +1/+1 counters on it and it becomes renowned.”

Renowned is a designation that has no rules meaning other than to act as a marker that the renown ability and other spells and abilities can identify. Only permanents can be or become renowned. Once a permanent becomes renowned, it stays renowned until it leaves the battlefield. Renowned is neither an ability nor part of the permanent’s copiable values.

If a creature has multiple instances of renown, each triggers separately. The first such ability to resolve will cause the creature to become renowned, and subsequent abilities will have no effect. (See rule 603.4)

If the effect of a resolving spell or ability regenerates a permanent, it creates a replacement effect that protects the permanent the next time it would be destroyed this turn. In this case, “Regenerate [permanent]” means “The next time [permanent] would be destroyed this turn, instead remove all damage marked on it and its controller taps it. If it’s an attacking or blocking creature, remove it from combat.”

If the effect of a static ability regenerates a permanent, it replaces destruction with an alternate effect each time that permanent would be destroyed. In this case, “Regenerate [permanent]” means “Instead remove all damage marked on [permanent] and its controller taps it. If it’s an attacking or blocking creature, remove it from combat.”

Neither activating an ability that creates a regeneration shield nor casting a spell that creates a regeneration shield is the same as regenerating a permanent. Effects that say that a permanent can’t be regenerated don’t preclude such abilities from being activated or such spells from being cast; rather, they cause regeneration shields to not be applied.