When Clackbridge Troll enters the battlefield, target opponent creates three 0/1 white Goat creature tokens.
At the beginning of combat on your turn, any opponent may sacrifice a creature. If a player does, tap Clackbridge Troll, you gain 3 life, and you draw a card.
If a player sacrifices a creature for any other reason (perhaps because it’s a Food and the player was hungry), Clackbridge Troll’s ability won’t tap it or cause you to gain life or draw a card.
When Clackbridge Troll’s last ability resolves, the next opponent in turn order chooses whether they want to sacrifice a creature at all and which creature to sacrifice if so, then each other opponent in turn order does the same, knowing the choices made before them. Then all the chosen creatures are sacrificed at the same time. If one or more creatures were sacrificed this way, Clackbridge Troll is tapped and you gain 3 life and draw a card—you don’t gain more life or draw more cards if more than one creature was sacrificed.