The comes into play ability triggers if at least one black mana was spent to play the spell as part of the generic mana cost portion. [D'Angelo 2006/01/22]
If the creature is put into play without having been played as a spell, no mana was spent to play it, so its ability won't trigger. [Guildpact FAQ 2005/12/22]
If a card such as Clone comes into play as a copy of one of these creatures, its comes-into-play ability will trigger if mana of the appropriate color was spent to play the copy card. [Guildpact FAQ 2005/12/22]