Assterion came to Castle Ravenloft during the events of Curse of Strahd in Spaaaaace!. While the party were able to defeat Strahd von Zarovich it was notable that Assterion took no part in the final battle.

After the events of Curse of Strahd in Space Asserion worked with the others to bring control to the castle and ensure that Strahd would not return… however as time passed his hunger grew and eventually he tried to feed upon his former allies causing a split in the party with some being eaten, others trying to flee into space and Koran fighting him off and banishing him to the lower portion of the castle.

He has since ruled over the ‘middle’ part of the Castle with enemies both below and above and after comitting to kill Strahd was instead defeated by the combined effort of Strahd’s summons and pet wolves. To add insult to injury Strahd staked Assterion though the heart using part of a old chair leg then summoned him to become the new Sir Bonesalot puppeting a unwilling Assertion as he explored his former castle.

Sadly for Assterion Strahd had caught the attention of Koran who in one stunning radiant attack destroyed Assterion’s remains completely leaving him as nothing more then a mind and scattering as dust.. still ‘aware’ as he remains a Dreadlord as long as some part of Ravenloft remains under his control.