If you control more than one creature with best in show, one of them becoming a target of a spell or ability you control (or a creature you control without best in show becoming such a target) will start a chain reaction
25 is still a lot
Too many decks fall apart when their Commander is subject to repeated removal, and Lightning Greaves protection from targeting and free equip cost will keep your key cards around for that much longer
Mentor compares the power of the creature with mentor with that of the target creature at two different times: once as the triggered ability is put onto the stack, and once as the triggered ability resolves
The second is that if youre building your deck to be dense with legendary creatures, which you really want to be doing with Kolvori in your deck anyway, the restriction on using the Crests mana is much less painful
A perfect way to embrace this holiday is by putting together one of the newest Disney Lorcana puzzles, featuring glimmers of Disneys Winnie the Pooh, Elsa, and Moana