This doesn't mean you should entirely ignore cards that cost less than four mana as there will always be some room to cast one, two, or three-mana spells, but you can afford to push your deck into the higher-costed cards with Ruby at the helm
Fyndhorn Brownie who's bursting out of a snowbank and lobbing snowballs at people
At first glance its 2-power-or-less prerequisite seems like an insurmountable downside, except when you consider how many great targets red has at that level
He loves when everyone gets to do their thing in a game of Commander and spends way too much thinking about game design
If, during a player's declare attackers step, a creature that player controls that's been goaded is tapped, is affected by a spell or ability that says it can't attack, or hasn't been under that player's control continuously since the turn began (and doesn't have haste), then it doesn't attack