We mainly care about the first trigger here, which at minimum lets you rummage away a card and force your opponent to discard a card, but it can do so much more
Imagine that a creature has two counters: an indestructible counter, and a finality counter
Your table definitely hates you for this one, particularly if you have it with Krark's Thumb
Although Counterspell has been a true contender in trying to substitute the discard spells, I think Thoughtseize is for Modern what Force of Will is for Legacy and Vintage
It can generate significant advantage through milling and Splendid Reclamation, but I wish returning lands to hand had been optional
Game Night: Free-for-All Commander Quick Look If you havent heard of it before, the Game Night product line is Wizards of the Coasts effort to make Magic more accessible to people who enjoy traditional board games