There’s a bright side to your favorite “Game of Thrones” characters getting killed off the show: Those actors have more time to go to fan conventions. For instance, GOT warlord Khal Drogo, a.k.a. actor Jason Momoa, is one of the headliners of this year’s Boston Comic Con. The convention revealed a list of VIPs on Monday, and announced that it has added a third day of festivities this year. From Aug. 8-10, the Seaport World Trade Center will be packed with fans getting close to stars such as John Barrowman of “Doctor Who”; Katie Cassidy of “Arrow”; Sean Astin of “The Goonies” and “The Lord of the Rings”; and James Marsters, who was Spike on “Buffy the Vampire Slayer” and “Angel.” There will also be a Cosplay Harbor Cruise on Saturday hosted by artist and costumer Ivy Doomkitty.