Yea no I'm still not normal about these two. Sorry.
Anyway! If Esther and Sultan were actually in the game, in the way I envision them, you could meet them in the unused big corner of the ark that Sultan decided to turn into a nice little potion shop.
How does a crab make potions with his tiny legs? Don't worry about it!
Basically, you can buy not-so-legal (I mean... can creatures even be held to the standard of law?) potions from these guys, including a potion that can transform you into a creature at any moment at any place, a potion that lets you understand creature language (after all, who doesn't want to hear the latest manta gossip!) and many other brews. There are many to choose from! And all are welcome (as long as you pay.)
Also, an additional doodle of these two relaxing after a long day of running the shop
(Yes I did draw Sultan bare-chested just to show off his crab-themed top surgery scars. This guy literally said "take my boobs and give me a crab army")