A Birds of Paradise from that sheet went for 4+k, and considering there are some huge dragon collectors (including the gentleman who owns the Shichifukujin and a couple of his friends) around, Im certain the Shivan breaks 10k
Commander players love tribal themes, but Wizards of the Coast has definitely been very uneven in support for specific tribes
Be warned: this card is a rules nightmare, so you might want to do a rules deep-dive before playing it
For instance, some of the most expensive Sword and Shield cards are composed of very popular Pokmon
That's right, this means that a Siege's controller can attack it with their creatures, and the opponent they chose as its protector can assign their own creatures to block those attackers
Both are important, and should probably be included in most decks