Additional Card Options Gear Golem the Moving Fortress, Gravekeeper's Spy, and Legendary Jujitsu Master are all respectable walls which protect the Countdown player should a floodgate fall
These are some of the most political cards in Commander, though there are plenty more to explore
The last angel Ill mention is Serras Guardian, originally from Core Set 2019
If you can find one or two at a garage sale, or a stash in someones attic, it can amount to major profit
Triggered abilities use the word "when," "whenever," or "at." They're often written as "[Trigger condition], [effect]." Some keyword abilities, such as mobilize (from the Tarkir: Dragonstorm release), are triggered abilities and will have "when," "whenever," or "at" in their reminder text