Some quick table napkin math will show you that this drop's not worth it at all from a financial perspective , assuming it's priced the same way most Secret Lairs are priced ($30-40 for nonfoil copies, $40-50 for foils, with this particular drop coming in rainbow foil)
Rules when playing with proxy cards [edit] Players who do not trust each other blindly will usually agree on common rules, defining which kind and number of proxies, if any, is allowed for each player
Also, Rosewater explained on his personal blog that all of the stickers are made with a very light glue (think Post It Note glue) that can be used numerous times and wont harm the card its stickered on. He also recommends using slips of paper, as long as the proxied sticker comes from the sheet the player pulled from their booster
Incapsula incident ID: 679000170039568026-149390331377812562
Finally, 12 multicoloured cards use menace
As a small bonus on top of that, it also gets a +1/+1 counter for doing it