Getting a creature from any graveyard each turn is a huge benefit for you, and youll know you have a couple of your opponents creatures to choose from thanks to this card forcing them to sacrifice a few
He isn't as big a threat as people though, but he is still an excellent Grixis (red/blue/black) Commander
Youll still want a nice bell curve of mana costs in your cards, but unless youre playing cEDH (competitive EDH, a hellscape where games end before youve even finished shuffling - fun, but in a horribly different way), you can have a bit more fun
If the target is illegal as Taskmaster's ability tries to resolve, it won't resolve and none of its effects will happen
Depending on the type, each set will normally have its own theme, either based around a particular fictional setting in the lore, or perhaps tailored to one particular mode of play, like the Commander or Modern formats
Enchantment tutors are the bread and butter of a shrine deck, and since everything you want to find is an enchantment, Idyllic Tutor and Enlightened Tutor are perfect