Normally youd just let it through, but then theyll draw a card, and you cant let that happen
Combined with Cauldron Familiar and any kind of sacrifice outlet, Samwise can create infinite Food tokens, and infinite damage, incredibly easily
I also like this with creatures that have a combat damage trigger that scales up with the combat damage dealt
The final core set (soon to be replaced with the 2nd set in the 2nd block of each season) is chock full of subtle and original cards that many players, both pro and amateur alike, have been having trouble evaluating
They can still tap for mana, so you aren't forcing them to have a bunch of Mountains out, but this is a nice and friendlier way to attack people who abuse lands precisely because they are harder to answer and people feel uncomfortable playing land-answers