Designing Ys, Vol. 2: Nygtilger

Ys I & II mark the beginning phase of Falcom's rubber-band level progression, though it was completely absent in earlier versions of the game. Stronger monsters up to par with Adol's level award more experience, while those beneath Adol award less, so as the player fights new monsters they'll find Adol's level "snapping" to the value the current dungeon is balanced for and then not budging any further. The function of this is made possible by giving each monster a prescribed maximum level at which Adol may obtain full experience from it—for every level over that, the EXP received is halved. For example, at level 9 Lyuses award 8 Experience Points; at level 10 4 EXP; at level 11 2 EXP; and at level 12 and above 1 EXP.

This allows each boss to be balanced for a specific point on the level curve, but because of both this and the subtractive damage formula, low-level runs range from impractical to impossible. Players can usually only function at the exact level specified for each area. The first boss of Ys is balanced for level 4; Nygtilger is balanced for level 10.

That's a significant gulf in experience, and it's facilitated by the layout of the first big dungeon. The player's progress throughout the Shrine relies on thoroughly combing the place over. None of the other treasure chests can be opened until they have the Treasure Box Key from the second basement floor, and Nygtilger's lair is double-gated behind doors requiring both the Ivory and Marble Keys, which are in locked boxes on the third and second basements. The Marble Key is further behind a door that can be only accessed with the Mask of Eyes, which can be found on the first floor but also requires the Treasure Key.

This model of progress—a kind of item checklist the player is gradually filling as they progress—is among the oldest tricks in the developer's book, akin to the item puzzles of Zelda or ability requirements found in Metroid. In Ys it's implemented with a specific purpose for how the game should play moment-to-moment: the continual retreading of past floors serves to bring the player in contact with more wandering monsters, which respawn the moment the player scrolls them out of view, building their character level up high enough in time for them to arrive at Nygtilger. As a resulting, there's no grinding. The player is already as powerful as they should be as soon as they arrive on the boss' doorstep.

The "centipede" as players so often call it is designed to draw the player into a chase. The head is the only part that can damage them, while every other segment is vulnerable to Adol's sword. Thus the player chases Nygtilger's tail while its head chases their own, causing the two to circle one another until they make a misplay and must break apart to find a new position to attack from. The fight contrasts strongly with the patient wait-and-charge pattern of Jenocres, and serves to reinforce a lesson about the nature of dungeons versus overworld areas. While the player was free to exit Jenocres' battle anytime and recover their Hit Points in the hallway, leaving Nygtilger's fight won't trigger the passive health regeneration because they're inside a dungeon area.

The battle can be over in seconds or minutes, but the longer it drags on the more likely the player is to fall, for one simple reason: Nygtilger is faster than them. This is the first of several unequal fights in Ys. In general, the difficulty of the game comes from how uneven the boss design is. Major enemies simply have more resources at their disposal, whether that comes in the form of greater speed or more angles of attack than the player. The simple fact that the odds are against them in protracted battles creates great tension for the player, but at times it can also be a weakness as one of Ys' strengths is its soundtrack, and because of these design sensibilities it can be rare to hear certain tracks ever fully played out.

Once the player has Nygtilger's vulnerabilities and pattern down, the fight becomes simple. However, this is the last fight where knowing such information can grant an easy victory. The next major battle serves as one of the defining gameplay moments of Ys I, and the reason that many players give up without seeing the game through.

Vol. 3: Vagullion

Nygtilger in the Ys anime series.