Triggered abilities are the most common kind of ability, with most keyword abilities (Lifelink, Magecraft, Landfall, Trample etc.) being triggered abilities as well
All these factors combined make Belle an absolute gem for any discard-loving player and a royal pain for everyone else
RENEWED SOLIDARITY Renewed Solidarity is such a monster pickup for white token decks, and its not even funny
And their ultimate draws you four cards and shoots folks and their dorks for at least four damage each, and likely lots more
Atraxa looks like a solid +1/+1 commander with some of the best commander colors avaible and really good stats, BUT there's no efficient combo with Atraxa who could win the game against 3 opponents nor does she provide you card advantage, where Zirda, the Dawnwaker for example is already one part of a efficient combo (Zirda + Basalt Monolith/Grim Monolith + a card like Walking Ballista), which makes it pretty easy to win fast with her as a commander