Ultra series

The Ultra Series (ウルトラシリーズ, Urutora Shirīzu^?) is the collective name for all the shows produced by Tsuburaya Productions featuring Ultraman, his many brethren, and the myriad Ultra Monsters. The Ultra Series is one of the prominent tokusatsu superhero genre productions from Japan, along with Toei produced series Kamen Rider, Super Sentai, and the Metal Heroes. The Ultra franchise is also one of the most well known examples of the daikaiju (大怪獣, "huge monster") genre, which also includes Toho's Godzilla series, and Daiei Film's Gamera series. However, the Ultra Series also falls into the kyodai hīro (巨大ヒーロー, "Giant Hero") subgenre of Tokusatsu shows.

Ultraman and his many kin are usually red-and-silver (although several color variations have been seen in recent years) and have glowing yellow almond-shaped dome eyes (although there are exceptions to both the shape and color) and various abilities, most notably to fire energy beams from various positions of crossed hands.

The Ultra beings' main weakness is that they can only stay on Earth in giant form for a limited span of time, usually not longer than three minutes, owing to a limited supply of energy (Earth's atmosphere filters out solar energy). This is marked by a light on the character's body usually called the Color Timer, or "warning light," which eventually begins to blink with increasing frequency as his energy supply dwindles (and turns from blue to red). At this stage, the Ultra beings must either find a way to recharge or finish the fight as soon as possible, or involuntarily revert to human form, or worse, risk certain death. Some say another reason for Ultraman to recharge is because the Earth is badly polluted by humans, so Ultraman only has three minutes on Earth, but can survive long enough in outer space. The time limit only happens inside the Earth's atmosphere but they have none of those setbacks outside. To counter this, Ultramen almost always merge with a human host or create a human form for themselves in order to survive on Earth, more often than not reviving a recently dead person with their own lifeforce. In other cases a large enough amount of energy can be utilized to bring them back to life, usually provided by their human allies, even after being completely destroyed, as was the case with Mebius' death at the hands of Empira, only to be revived shortly thereafter by the life energy of his allies.

...
Wikipedia