Flying
When Tiamat enters, if you cast it, search your library for up to five Dragon cards not named Tiamat that each have different names, reveal them, put them into your hand, then shuffle.
A Dragon card is a card with the creature type Dragon in its type line. A card that has “Dragon” in the name (such as Dragon's Disciple) isn't a Dragon card unless it also has the Dragon creature type.
23 Jul 2021
Tiamat's enters-the-battlefield ability will trigger if you cast Tiamat from any zone, not just from your hand. Still thinking command zone over here.