Dragon tongue in Harry Potter fanfiction can also be a symbol of power. Characters who possess dragon tongue or know how to use it are often seen as more powerful or special. For example, a powerful dark wizard might be seeking dragon tongue to increase his already formidable powers, while the good guys are trying to stop him from getting it.
Well, Harry could marry one of the veelas. Given their beauty and allure, it would add an interesting dynamic to the story. Their relationship could involve Harry having to deal with the jealousy of other wizards and also the cultural differences of the veelas. Or he could marry a descendant of one of the founders of Hogwarts. This would tie in a lot of Hogwarts history into their relationship, and their wedding could be a grand event that unites different factions within the wizarding community who have ties to the founders.
Maybe Dumbledore, if he were still alive in the fanfiction. Dumbledore was highly respected and had a great influence. Knighting Harry would be a way for him to publicly recognize Harry's achievements and heroism on a grand scale.
One possible plot could be that Harry uses his magical knowledge to create a bar with unique magical drinks. For example, he might serve Butterbeer with an extra kick of magic, or a potion - like cocktail that gives temporary magical abilities. He could also use the bar as a place for magical creatures and wizards to mingle, creating a new social hub in the wizarding world.
Hermione Granger is a very common character. Since she is Harry's best friend, she would likely be there to help him understand and control his new superpowers. She might research in the library to find out how these powers came about and how to use them effectively. Ron Weasley is also common. He would probably be both in awe and a bit jealous of Harry's new powers at first but would still support him in the end.
It could be Voldemort. He might use hypnosis as a new way to get to Harry, trying to make him a weapon against the Order of the Phoenix. Another possibility is a new dark wizard who wants to make a name for himself by controlling Harry Potter.
It could be Dumbledore. Dumbledore is always full of surprises and he might give Harry the staff as a last - resort weapon to fight against Voldemort. He could have been secretly researching the staff and its powers and decided that Harry was the only one who could wield it properly.
No. Fanfiction that involves such inappropriate and sexual content is not acceptable in the Harry Potter fandom. The Harry Potter series is mainly aimed at a wide range of audiences including children and young adults, and this kind of content goes against the spirit of the original work which is about magic, friendship, and heroism.
It could be Hagrid. Hagrid is always looking out for Harry and giving him things. He might come across this special trunk during one of his travels in the Forbidden Forest or in some wizarding market and think it would be perfect for Harry.