Rumors abounded that MissingNo could cause permanent damage to the game or save file, but these were unfounded, in retrospect
Further Upgrades The first cards I'd pick up to further juice up the deck would be untapped mana-fixing lands: Watery Grave, Shipwreck Marsh, Underground River, Morphic Pool, Darkslick Shores, Polluted Delta, Sunken Ruins, Undercity Sewers, Urborg, Tomb of Yawgmoth and then maybe a couple more Island / Swamp fetches
The Basic Water Energy card powers Water-type moves
MTG Cardsmith MTG Cardsmith is fine
Pokemon Mystery Slabs We sell Pokemon Mystery Slabs and Pokemon Mystery Graded Cards
Equip Artifact - Equipment Warrior's Sword Job select (When this Equipment enters, create a 1/1 colorless Hero creature token, then attach this to it.) Equipped creature gets +3/+2 and is a Warrior in addition to its other types