Middle Earth: Shadow of Mordor - Black Celebration - Poison a Captain at his own Feast. [Bronze / 15G]

Before trying this you must have beaten the Story mission called "The Outcasts"! This is one of the early missions and it will grant you the Poison ability. Without it you cannot obtain this trophy / achievement.
Feasts randomly show up on your map and are marked with a red icon. If no Feast is available then scroll over a Forge Tower on your map and advance the time. This will make new events spawn. Do this until a Feast appears.
There are multiple drinking bowls in each Feast. The Captain will walk from one bowl to the next. You must poison one of them without being seen and wait for the Captain to drink from it.
If you are detected you must quit the game to try the event again!