In Commander, that means it can generate multiple face-down creatures every turn cycle
Shes just so far beyond or above it all
Its entire purpose is to be a higher-priced luxury set, akin to Modern Horizons 2 or Commander Legends before it
In other words, you have to activate or cast the ability or spell that grants regeneration at a time when you have priority, or under some condition spelled out by a static ability regenerates text
Many of the best white creatures include abilities that force your opponent to play around additional costs, can swarm the board with all sorts of little creatures, and control the skies with flying creatures like angels
Liliana of the Veil has maintained a good value since its release thanks to its power in formats like Commander, making the SDCC version all the more valuable among players.