At the beginning of your upkeep, investigate
If you have enough mana to cast this you don't really need its ability
Capable of being reliably cast within the first turn of any game, Yoshimaru is a 1/1 legendary dog that gains a +1/+1 counter whenever a legendary permanent enters the battlefield under its owner's control
It can, for example, recognize cards on textured backgrounds (the image of the Dragon Whelp below), cards in sleeves and cases (Counterspell in the BGS case), several cards in one image (picture of my Wizards Tournament II Blue-Red counterburn deck), and cards photographed in a an extremely tilted angle (the last three images below)
Some shops even carry vintage cards for those seeking rare finds
You want to see what your collection is worth and what a deck will cost to complete