Servant of Thrones (サーヴァント オブ スローンズ) is a free-to-play social game. Its centers on Lords, or people who make soul contracts with spiritual entities, in a fantasy world. General gameplay is a mix of card decks and real-time tower defense.
On March 14~29, 2018, players could participate in a set of Drakengard collaboration quest, the second game in the Yoko Taro collaboration series. Other Yoko works include NieR:Automata and SINoALICE. Players can complete these quests to earn Angel Points, which can be exchanged for additional items. The full version of Tsukiru played in-game for the quest notices and music from Drakengard plays during the maps.
The prologues for each set of quests has Peter (Japanese voice actor for Angel) narrate weapon stories that are related to the key characters for the collaboration: Caim, Leonard, and Arioch. The voiced narrations are exclusive to this game.
Logging into the game during the collaboration's runtime will reward players with the Lord of Vermilion versions of Caim, Leonard, and Arioch. They could additionally be earned through the limited time gacha or played temporarily through the fixed deck event maps. All cards recycle their Lord of Vermilion voice clips. Caim is LE (legendary) status and the most durable of the trio since he is summoned while riding Angel. When she falls, he dismounts and continues charging towards the enemy camp.
Along with the in-game collaboration, Square-Enix launched three Twitter campaigns that randomly awarded a special T-shirt, Peter's autograph, or Drakengard themed smartphone cases. All campaigns expired by March 31, 2018.