Flelf

 This card's name is a palindrome.

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This could be related to Celtic Guardian (Elf Swordsman in OCG) in the way that Gagaga Magician relates to Dark Magician, possibly referencing that Yuma Tsukumo is a successor of Yugi Muto.

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This monster is very similar in appearance to Shining Elf.

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This is supported by the fact this is a Level 2 monster and Shining Elf is a Rank 2 Xyz Monster, which makes usable for that Xyz Monster.

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OCG Rulings

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Revealing one Monster Card from your hand is an activation cost.: Effect Monster > Flelf

The increase to "Flelf"s Level disappears if "Flelf" is banished or flipped face-down.

When resolving the effect of "Flelf", if the revealed monster is not in your hand, then you still apply the Level-increasing effect.: Do you still increase the Level of "Flelf" if the revealed monster is not in the hand when when resolving the effect?

After the effect of "Flelf" resolves and increases its Level, if "Flelf" is flipped face-down by "Book of Moon" or banished by "Interdimensional Matter Transporter", then you no longer apply the Level-increasing effect.: After you increase the Level of "Flelf", if it becomes face-down or is banished, then does the Level return to its original value?

After the effect of "Flelf" resolves and increases its Level, if the revealed monster is no longer in the hand, then the Level of "Flelf" remains increased until the End Phase.: After you increase the Level of "Flelf", if the monster you revealed to your opponent is no longer in the hand, then does the Level return to its original value?

If you activate "Cost Down" and then activate the effect of "Flelf", then the Level of "Flelf" increases by the revealed monster's decreased Level.: If you activate the effect of "Flelf" by revealing a monster whose Level has decreased due to "Cost Down", then do you increase its Level?
Example: If you reveal a monster whose original Level is 4 but is currently treated as Level 2 due to "Cost Down", then the Level of "Flelf" increases by two.

If "Enemy Controller" is Chained to "Flelf"s effect so that your opponent controls "Flelf" when the effect resolves, then you still apply its Level-increasing effect.: Does "Flelf"s Level increase if your opponent controls it when its effect resolves?