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• If the Resourceful Rat takes an item or gun, he will give another item or gun of the same type and quality. The Rat can be traded with once per floor after acquiring the ring. Unused trades will carry over to subsequent floors, allowing multiple trades on a single floor to be possible.

• If the player lets the rat steal the Bullet That Can Kill The Past without picking it up first, it will be replaced with an passive item. The rat will not take the Bullet That Can Kill The Past if the player is in a [Clone] run and already has one equipped.
• "Unranked" items, such as starting items, Glass Guon Stones , or [Junk] , will be taken by the Rat without him leaving any items in return.
• For items that can be found in multiple ranks of chests such as the various heart containers or [Finished Gun] , the rat will trade them for an item of their highest rank. Occasionally though, the heart container items will be traded for B-rank items instead. Do not rely on trading them away as a method of obtaining A-rank items.
• The Resourceful Rat will not trade with the player if they have the Resourceful Indeed synergy. The Resourceful Rat will, however, still trade with the player without the synergy even if they have beaten him in the Punch-Out!! phase of his boss fight. In this state, he will not steal if all trades are used up, however he will still steal certain pickups.
• While playing a Rainbow Run , if the Resourceful Rat steals an item from a rainbow chest, the other seven items will disappear; thus, only one item per chest can be traded.
• The Resourceful Rat always trades with the latest item that qualifies for trading (most recently dropped).
• The Resourceful Rat will not trade with the player while in the Resourceful Rat's Lair .
• Trading is triggered the same way that the Resourceful Rat usually steals from the player; that is, by dropping an item or gun in a room and then leaving the room for a few seconds.
• If you have more active items than you can carry, the rat may initiate an unwanted trade. You can rid yourself of the extra active item by dropping it in a pit to avoid unwanted trades. If a trade is done by mistake, simply avoid picking up the new active item and the rat will not steal it again wasting more trades.
• The Resourceful Rat will not trade active items with passive items and vice versa.
• Once the Rat cycles through every gun or item (depending on what was traded) of one quality, he will cycle through guns/items of one tier lower. This includes [Clone] , obtained from trading with the Rat or otherwise(ex. from [Weird Egg] ). During a [Clone] run, the Rat will cycle through unobtained S tier guns/items, excluding [Clone] .
• Unused trades from a previous life with the [Clone] will not carry over after death.
• Unsued trades will be lost if the game was saved and quit using the save button. Despite this, the Recourceful rat will remember items he gave you even through saves. It is therefore over the single run never possible to obtain any one item twice with the ring
• If duplicates of this item are somehow obtained, allows one additional trade per floor for every extra duplicate.
• For some reason, the description of this item in the Japanese version gives a completely different explanation. Interestingly, there are no other items with this described alternate functionality. Here is the original: イヒヒヒヒ! かしこいネズミがはめていた指輪。 感覚がするどくなり、ふつうなら見落とすようなものにも気付ける。 そうびすると、たいていの毒を浴びてもダメージを受けなくなり、1度だけなら死を免れることもできるという。
• And here is the translated version: Ihihihihi! A ring worn by a smart mouse. I feel sick and notice things that I would normally overlook. If you do so, you will not be damaged by most poisons, and you can escape death only once.

Defeat the first two phases of the Resourceful Rat .