Thats perfectly fine, and if you can keep attacking with evasive creatures, you can potentially draw a lot more cards without paying any mana, which is a great deal
It could be fetching Rest In Peace to stop Karador, Ghost Chieftain from running wild, or Oblation to tuck Erebos, God of the Dead, or Mind's Eye to start drawing tons of cards
Similar to past Standard set released Jumpstart booster packs, there are five themes (one for each MTG color), with two variations per theme for a total of 10
But did you know that instants arent the only spells you can cast on your opponents turn
The only problem with Magus of the Mirror is its cost, at 6 mana, and its lack of immediate impact on the board, since it needs to wait a turn before it can tap and activate