Black Luster Solider has this... thing... written on its card:
Ritual: You may move a monster from your reserve pool to your used pile to pay this monster's summoning cost.
So what is this? Is it a Global? It is written in red like Globals. Is it something else? What is the timing on its use if it is something else?
The Yugioh rule book does not define "Ritual", doesn't even mention the word at all, so that's why I am calling it a thing for now.