REDU format ruling
Mystic Swordsman LV6

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)Cannot be Normal Summoned (but can be Normal Set). At the start of the Damage Step, if this card attacked a face-down Defense Position monster: Destroy that monster, and if you do, you can place it on top of your opponent's Deck instead of sending it to the Graveyard.
Rulings
- The Normal Summon (Tribute Summon) of this monster is the same as, and always considered, a Tribute Set. This card must be in face-down Defense Position when it is Normal Summoned (Tribute Summoned). If you Normal Summon (Tribute Summon) this monster, it is placed face-down on the field; you do not have to show your opponent what monster it is.
- If your Mystic Swordsman LV6 destroys your own monster that is being controlled by your opponent, that monster is sent to the GY. You cannot return it to the top of your opponent’s Deck or the top of your own Deck.
- If you activate the effect of Mystic Swordsman LV6 to place a face-down monster on top of your opponent’s Deck, you do not get to look at it.
- If Mystic Swordsman LV6 attacks a face-down monster, its effect activates at the beginning of the Damage Step, before the monster is flipped face-up. If Ceasefire was activated during the Battle Step to flip the monster face-up, then the effect of Mystic Swordsman LV6 is not activated.
- A monster destroyed by the effect of Mystic Swordsman LV6 is not destroyed as a result of battle. There is no damage calculation. It is not flipped face-up. Any Flip Effects it has are not activated.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.