REDU format ruling
Elemental HERO Chaos Neos

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)"Elemental HERO Neos" + "Neo-Spacian Dark Panther" + "Neo-Spacian Glow Moss"
Must first be Special Summoned (from your Extra Deck) by shuffling the above cards you control into the Deck. (You do not use "Polymerization".) Once per turn, during the End Phase: Shuffle this card into the Extra Deck, and if you do, Set all face-up monsters on the field. Once per turn, during your Main Phase 1: You can toss a coin 3 times.
● 3 Heads: Destroy all monsters your opponent controls.
● 2 Heads: For the rest of this turn, the effects of all face-up monsters your opponent controls are negated.
● 1 Head: Return all monsters you control to the hand.
Rulings
- Monsters Set by the effect of "Elemental Hero Chaos Neos" are Set in Defense Position.
- "Elemental Hero Chaos Neos" can be Special Summoned from the GY if it was first Special Summoned according to its text and sent to the GY afterwards. "Elemental Hero Chaos Neos" can also be Special Summoned from the Removed Zone if it was Special Summoned according to its text and then removed from play afterwards.
- If "Elemental Hero Chaos Neos" is destroyed before it can return to the Extra Deck by its own effect, the effect of Setting every face-up monster on the field disappears.
- You can activate the coin toss effect of "Elemental Hero Chaos Neos" even while there are no monsters on your opponent’s side of the field.
- If you activate the coin toss effect of "Elemental Hero Chaos Neos" and get 2 Heads, if "Elemental Hero Chaos Neos" is flipped face-down or removed from the field the effects of all face-up monsters on your opponent’s side of the field will still be negated.
- The effect of returning "Elemental Hero Chaos Neos" to the Extra Deck and Setting all face-up monsters on the field are one effect. If "Elemental Hero Chaos Neos" is not returned to the Extra Deck (because of "Neo Space", etc.) face-up monsters on the field will not be Set.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.