The Quest of Ki

The third game in the Babylonian Castle Saga franchise, the first to be made exclusively for a console and a prequel to its initial entry (the Tower of Druaga) that explains exactly how Ki got to the top of that tower; a logical expansion after the first and second games chronicled Gilgamesh's trip up the tower to save her and the second showed their escape.  Quest of Ki also marked another changeup in gameplay for the series - exhuming the RPG elements and, indeed, even disposing of combat entirely, Quest of Ki is a pretty simplistic puzzle-platformer, with the twist that you can continue to gain vertical height indefinitely as long as you hold down the jump button; however, if you hit your head on a ceiling, you'll drop straight down and be left in a vulnerable state until you've touched the ground for about a second, so careful control of your movements is required.  A few nods to the original puzzle-driven game still remain, though - you still have to collect a key to open the door and exit the stage, and you can collect powerups that aid you in various ways.  To name a few, there are candles that make ghosts visible, a sleep spell that temporarily renders some enemy types harmless, and wings that grant temporary flight (allowing you to 'jump' in midair).  Perhaps taking a couple of cues from Mario, you can also find hidden warps that skip you ahead several stages, though once you hit the bonus levels they'll start sending you backwards instead.  Overall, not one of the Famicom's more memorable platformers or puzzle-driven games, and as it's not even really an RPG, it only gets special mention on this site because of its status as a prequel to two of them.  If you're absolutely set on playing all the Babylonian Castle Saga games this is your first stop chronologically, but everyone else should probably pass it up in favor of something more enjoyable.

Developer: Game Studio
Publisher: Namco
Released: 1988
Platform: Famicom

The Return of Ishtar

The direct sequel to the Tower of Druaga in the most literal sense - it starts exactly where that game ended, following Gilgamesh and Ki as they attempt to escape the tower.  Return of Ishtar is probably the very first co-op action RPG ever made, and I do mean co-op - having two players at the controls is required to play!  Thankfully, the game's action is considerably more straightforward than the puzzle-driven experience the first one provided, having Gilgamesh battle enemies in melee range (with touch combat similar to Hydlide or Ys) while Ishtar battles enemies at range with spells; however, if either player dies, it's a game over and you must spend a quarter to continue.  The layout of the dungeon is also considerably more complex; there are still 100 maps to go through, but now they're interweaved with multiple exits that can take you forward or back to previous rooms, so it's still a very long and involved process to complete.  Thankfully, you don't have to go through the whole thing in one long sitting - a password system keeps track of your progress through the dungeon.  It's also a fairly unbalanced asymmetrical experience - Gilgamesh's health drains when he attacks, making him completely dependent on Ki's healing to survive, while Ki gets all manner of ranged attack spells, supportive spells, buffers (including some that give Gil his only means to even harm certain types of enemies) and healing spells, and the camera only tracks her movement.  Basically, Player 2 just ends up being a glorified meatshield for Player 1, who dies in a single hit.  Worth a try for RPG historians as an interesting period piece that would lay the groundwork for co-op RPGs down the line, but there are many better such experiences to be had today.

Developer: Game Studio, Namco
Publisher: Namco
Released: 1986
Platforms: Arcade, FM-7, MSX, PC-8801, PC-9801, Sharp X68000, emulated versions are available on Namco Museum Volume 4 and as part of the Arcade Archives series on Switch.