They will protect your cards, and can be used for your rare cards or deck that you don't want to damage
There are a tremendous number of ways to do this, so things can be a bit overwhelming at first
Abyss Proxy Shop offers premium Lolth, Spider Queen MTG proxies printed on German black core paper, the same weight, size, and thickness as authentic Magic: The Gathering cards
That first ability resembles the shenanigans you can get up to with Dargo, the Shipwrecker, so in the right deck, you can cast it for two mana, attack for seven (that can only be blocked by legendary creatures), and then sacrifice it to destroy an annoying artifact or creature
Each card contains specific signifiers that dictate its game-loop usage and collector classification
Buy single cards you want to use from a third-party vendor