mtg all gate cards Colossus (Card) untap all attacking creatures Open the Gates | Ravnica

Its an odd card, but despite it seemingly being way too expensive, its actually normally only going to cost you one mana, because its one generic mana cheaper for each Creature on the battlefield

At least, until it has a friend

only and only while supplies last.

Adeline, Resplendent Cathar applies pressure very quickly if she comes out early with Goldbug, Humanity's Ally on the battlefield, while Rick, Steadfast Leader is a decent anthem and gives all of your Humans good abilities

Vitu-Ghazi Guildmage is in the list to be a populate-on-demand effect

Obviously these sorts of effects are much less exciting when they cant target opponents directly, but some are worth a look for efficiency or synergy reasons Dire Flail and Hunters Talent come to mind