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The guard and Keychain are rose-like, with thorns and roses that decorate it. The teeth seem to be claws which represents the owner of the rose, The Beast. It could also be to represent how much the Beast wants to protect the Rose. The rose based design is based on the Beast's Rose.
Rumbling Rose is a pun on "rambling rose", a type of flowering shrub native to Japan and China that was imported into North America and has since become an invasive plant.
With a strength bonus of +5, it is tied with certain other Keyblades for the third highest strength increase. It is especially useful in Valor Form, since it allows an additional finisher to the combo.
 See also