I personally wonder if it's at all possible to add in the capability of vore for the character you've already added this concept with the Lost serpent consuming the character and gaining muscle from them. What if it could be done in reverse except considering the fact that you have the character essentially doing sounding using their cock either on the serpent or the serpent cock on the character. What if the character could consume the Lost serpent entirely into their cock and potentially begin a process of de-corrupting the lost serpent in way of consuming the corruption. Essentially the way I see it working is the serpent is taken into the character and then for a three or four turns the character churns the serpent in there balls absorbing corruption into themselves for a period of time and removing it from the serpent completely but in this process the character could also corrupt other creatures using their own cum and swallowing the characters into their ball's and corrupting them to the side of the character essentially they would become devoted followers of the character rather than being lost or some other creature potentially even changing the creature significantly. The character could also obtain the ability to swallow other characters into their stomach reducing the amount of bulk that the opponent has as a type of attack if the character has enough power to do so this would not entirely be about size this would be about power but the size would mean a significant boost in power for this skill.
Another concept I was thinking of was with the Nyx creatures if the character is large enough rather than them being consumed through the mouth and added to the character they could be consumed through the cock and go straight into the balls. Another thought I had is what is the slime could be added to the character as a addition similar to the bind ring or echo where it creates modifications to the character for instance the slime could make it to where the characters cum becomes sticky or extremely adhesive allowing for sigils to remain after being used and eventually it could be that the opponent becomes permanently marked by those sigils is hit with them enough time. Another way to sign could be beneficial to the character is that rather than just binding the schedules permanently to some opponents the slime could assist in binding the sigils together similar to the multi-sidual that Torgar has as an ability. Maybe the bastion should have a way to cleanse corruption through Able maybe with that the character could remove corruption if they start becoming corrupted to where they don't have to wait they can specifically select this and they will be in a process of removing the corruption completely from the character this process may not even affect echo for the simple fact it is a symbiote rather than a parasite like the corruption seems to work. There could be the ability to compact muscle essentially after you reach a certain size you can select an option at home you must have echo to do this but the way it won't work is that for several terms or cycles whatever term is used to represent days the character will be placed specifically in echo's form and the main body echo will then compact the muscle making it much denser and much smaller and depending on how high your size is the character can actually become significantly stronger and larger another thing is that depending on the size of the character when they begin the process they could select the process to be done more than once for instance if they are at godlike muscle size it could specifically be set to where the character returns to Herculean the character could still maintain their height and it would actually be encouraged that the character does to cut back the risk of the whole black hole idea another person suggested even though that would be an eventual possibility. Potentially the way this could work is that echo and the character have to train at the meteor site and that brings them closer together allowing echo to do more involving the character similar to the bind ring and training and sparring and growing the imp