If there was ever an obscure prototype it's Wizard. Wizard was supposedly the last of Atari's last 2K games, but went unreleased in favor of the new 4K games. Since Wizard was never advertised in any Atari catalogs and it was never assigned a part number, most people don't even know if its existence.
Wizard can best be described as a cross between Berzerk and Wizard of Wor. You control a wizard (at least I think he's a wizard), who must attempt to destroy the swirling star shaped creature. The board layout is a giant maze, which makes it hard to run from the creature and to get a clean shot off. Unfortunately the creature can move through the maze walls, but thankfully it can't shoot through them. Once you take a shot you'll notice that your wizard dims a bit, this means you are recharging, and cannot shoot. Once your wizard is done recharging he will light back up again, and you can take another shot. You don't have to worry about aiming you shots, as you will automatically shoot in the direction of the creature. This makes it easy to run away but still take shots at the creature.
The creatures damage counter is on the left side of the screen. Each time you shoot the creature it will take two points so damage and be stunned for a few seconds. This is your chance to get away to a safe distance and hide as you recharge. The creature is normally invisible unless it's shooting at you or it has taken a hit. You can tell where the creature is by listening to the "heartbeat" in the background. The closer the creature, the louder the sound.
If you manage to get the creature's damage counter up to 99, it will turn black and die. Your victory is short lived however as a new and more deadly creature will replace the old one. Each new creature starts with less damage than the previous one, and moves and shoots much faster. Each time you kill the creature your kill counter (next to the creatures damage counter) will go up by one, and your damage counter will go down significantly.
Wizard has a unique two player feature where one player can control the wizard while the other player controls the creature. Since the creature is normally invisible, the second player must move blindly about the maze until he comes in range of the wizard. The second player's creature will automatically fire at the player making his job slighty easier. This interesting twist on the normal two player variation shows some innovation not seen in many games.
Hidden in a random part of the maze is a small glowing flame. If the left difficulty switch is set to A then you Wizard has the added task of defending the flame. If the creature touches the flame your wizard will slow down as his source of power has been captured. On the easy setting the flame is invulnerable to the creature and doesn't have any affect on the game.
While Wizard may not look like much today, it's amazingly fun in short bursts. Unfortunately by the time Wizard was ready to be released (1980), Atari was starting to make 4K games with better sounds and graphics than their 2K predecessors. According to programmer Chris Crawford "It didn't fit well into the product line". Wizard was simply too dated to be released as is, but probably could have been made into a decent 4K game had Atari wanted to take the time to retool it. But as they say, time waits for no man. Sadly Wizard was left in dust, destined only to become a footnote in prototype history.