Pokemon Card 151 (sv2a) is a Japan-exclusive powerhouse
Any sort of Overrun effect without a way to push damage through is always a little suspect, though, so I don't think this will be a serious player, but giving all your creatures +10/+10 is pretty iconic
But I would move Serperior into play if you are late in the game and you get a grass Pokemon on your bench that you really want to use right away, you could then use Serperior's Leaf Tornado and get the necessary energy cards on that Pokemon you just put on your bench and retreat Serperior the next turn for only one energy and put that Pokemon into play with the necessary energy cards on it
Do not hesitate, you always use your Leader ability to take one Don on 3 or 4
Similarly to Seven Dwarves from Throne of Eldraine, Nazgl allows players to break a formats deckbuilding rules
By including versatile removal spells like Swords to Plowshares, Beast Within, and Vindicate, you can efficiently deal with opponents' threats and maintain control of the battlefield