Revival Cube

The Revival Cube (復活キューブ Fukkatsu Kyūbu) is a drug created by X Aphro alongside his other invention, the Gender Tablet, while he and Spike spent their two years of training during the time skip on Drum Island with Kureha. While the Gender Tablet was created solely for Aphro's use, Aphro managed to learn from Kureha in how to reproduce a similar drug to Chopper's Rumble Ball, in the hopes of creating something to help make Spike stronger. After the time skip, Spike is introduced as having learned how to use the Revival Cube and the effects it produces within Spike's body.

Usage
As the Revival Cube took inspiration from the Rumble Ball, it holds very similar effects to that of its predecessor. Like the Rumble Ball, upon being eaten, the Revival Cube distorts the "wavelengths of transformation" within Zoan type Devil Fruit users; granting them four additional forms to choose from. However, unlike the Rumble Ball, which lasts for only three minutes at a time, the Revival Cube has amazingly shown it can outlast the Rumble Ball for an extra two minutes, thus extending the usage of the Revival Cube to five minutes at once.

Shortly after returning from his training with Aphro, Spike had a tendency to shout "Revive" (復活させる Fukkatsu sa seru) before consuming the Revival Cube.

Side Effects
As Aphro has mentioned upon returning from his homeland, Sakura Kingdom, the Revival Cube is so closely similar to Chopper's Rumble Ball, that like the Rumble Ball, the Revival Cube is to be treated with extreme care. This is because distorting the powers of a Devil Fruit is exceedingly risky and dangerous.

Spike's usage of Aphro's Revival Cube is limited to six hour breaks in between the five minutes of transformations. This is because if two Revival Cubes are eaten within six hours, the ability to transform becomes harder to control, which can be disastrous in battle. Worse yet is when three Revival Cubes are swallowed within six hours, which causes Spike to become a nigh-unstoppable monster, which is aptly dubbed "Monster Shift."

The time in which Spike spends in his Monster Shift is undetermined. In this state, Spike can no longer recognize friend from foe, and loses all control over himself, making him a massive threat to be around. Furthermore, Spike also puts himself in danger when in Monster Shift, as the form robs him of vast amounts of stamina over time, which can potentially kill him if left unchecked. So far, there have been only two methods known to negate Spike's Monster Shift. One is to submerge him underwater, and the other is to attach seastone to his body, which both reverse the effects of Monster Shift; returning Spike to his default human state (dubbed "Man Shift.")

Trivia

 * The Revival Cube was obviously inspired by the Rumble Ball, which is famously used by the Straw Hat Pirates' doctor, Tony Tony Chopper. To differentiate it from its inspiration, Wyvern 0m3g4 attempted to change its appearance to that of a square, instead of a sphere. He was also under the belief that it resembled tofu squares at the time, which he believed to be humorous enough to throw in to the Revival Cube's design. Likewise, he announced the Revival Cube would be pink in coloration, which would seem out of place when used by someone like Spike, who Wyvern 0m3g4 attached the concept of manliness to.
 * The name of the Revival Cube was inspired by Spike's Ancient Zoan Devil Fruit, the Dino Dino Fruit, Model: Kentrosaurus. When deciding upon the name of the drug, Wyvern thought of a fossilized dinosaur being revived and given new life, and in turn, applied this idea to rejuvenating a person's body with newfound strength; which the Revival Cube does, by granting Spike extra transformations for his usage.