The ceiling on it is arguably above Lingering Souls but it is a lot less convenient to setup in getting there
This card reminds me a lot of the Heros Association card we got with One Punch Man, only its stronger, letting you both search for a card and play one for essentially free
Braingeyser will let you refill your hand as needed at this point, and you should be able to generate infinite mana, infinite Shivan Dragons, or the opportunity to fire off infinite Braingeysers at your opponents
Not only must you defeat him in the Merged World before he can be used, but he'll use Zantetsuken against you if you take too long
Its important to become intimate with at least the basic terms to always stay on top of whats happening on the field
Aside from link monsters who physically cant be turned to defense position, this guy puts a stop to every single monster out there