Malibu12s said:

Rematch essentially replaces your pet journal, as I understand it

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Yes it does and no it doesn't. Rematch gives you a toggle in the pet-journal which disables it completely thus restoring the blizz journal. From that point on you can use rematch in a standalone window.

I'm sorry to say that to my knowledge (I've just tried with Murkablo) all Blizzcon pets are not cageable. The only way to get them is by buying an unused code on Ebay. (for Murkablo my first google hit gave me a link to one that costed approx 197 euro). So you prolly don't need to be thinking about ...