Talisman: Digital Edition

Based on the wording of the achievement, you would need to access the center of the board and fight and kill a player who is already there.

However, the actual rules are a little more permissive. I was in the middle of a battle with two other characters in the Crown of Command, the Ghoul and the Minstrel. During his turn, the Ghoul attacked the Minstrel and dealt one last blow, killing him on sight. The achievement unlocked for me, even though my character wasn't the one who killed the Minstrel.

So as long as another character dies on the Crown of Command while you are there, you might very weel be awarded the achievement.