It works on one-shot Normal Spell and Trap Cards in addition to all the Continuous/Field/Equip Spells and even cards in Pendulum Zones
Given that Mega Evolution is expected to mainly contain cards from Japan's Mega Symphonia and Mega Brave sets, it seems almost all of these Mega exs have now been confirmed in one form or another
Even if it's not, it can be used as an Xyz material for this card by a shared effect, making it easy to have 2 materials
Maximizing Fell Stinger requires sacrificing a creature to its exploit ability, but in return, you get to draw two cards at the cost of losing two life
Long gone are the days of finding those extra little clauses from R&D expressing their ideal use cases for their designs, or spotting snippets of worldbuilding blending into rules text
Whether for trading at your next game night or as a decorative piece in your Pokmon shrine, these cards shine in every aspect