REDU format ruling
Slip Summon

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)Activate only when your opponent Summons a monster. Special Summon 1 Level 4 or lower monster from your hand in face-up Defense Position. Return it to the owner's hand during the End Phase.
Rulings
- This effect does not target. You cannot activate this card during the Damage Step.
- If you use "Slip Summon" to Special Summon a monster like "Elemental Hero Wildheart" that is unaffected by Traps, it will remain on the field and not be returned to the owner’s hand during the End Phase.
- The effect that returns the Summoned monster to its owner’s hand during the End Phase does not start a Chain.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.