A pulsating cyan cube that is occasionally dropped by enemies. When picked up, it restores John's health vial. These cubes also appeared scattered about in the Land of Wind and Shade. While , the gel was the main healing item if he got injured by the various enemies in the game.
By ascending rungs on the Echeladder, John raised his 'Gel Viscosity.' This stat appears to make it more difficult for enemies to knock his Health Vial out of the gel that contains it, hence the name. It's analogous to a defense or stamina stat.