Ion Cloud (also known as Anion in the SNES/PS version) is an enemy in Chrono Trigger. They appear in the Hunting Range in Prehistory. Mostly amorphous blobs of black goop, these creatures exhibit some humanoid features such as mouths, eyes, and arms. Occasionally, they curl up into puddles, which increases their Defense. Attacking them should cause them to unfurl into the true form. Acid share similar palette forms with Alkali, Shadows, and Acid, and often accompany large groups of them in battle. The main difference is the color. Acid are orange, Shadow are purple, Ion Clouds are black, and Alkali are green.
It's important to note that technically, there are two kinds of Ion Cloud. They have the exact same appearance and stats, but one drops 2 Feathers (which are also Charmable), while the other drops 2 Petals (again, Charmable).