Its enter-the-battlefield effect to deal five damage to a creature directly feeds into the other effect relating to excess damage
Jolrael, Empress of Beasts Discarding two cards feels like an immense cost that makes me wary of playing Jolrael, Empress of Beasts, but making your entire mana base into 3/3s threatens tons of combat damage
Meren gives you an experience counter whenever a creature you control dies, meaning its very easy to generate a huge number of these counters in a sacrifice deck
Is 3 damage your priority, is instant speed more important or costing one mana
You get premade decks that are genuinely quite playable, interesting and fun
The ability to pay mana and ping each opponent isn't incredibly powerful, but it is a way to keep things rolling in decks such as Rakdos, Lord of Riots or the more recent Ob Nixilis, Captive Kingpin without having to have spells or other nonland permanents around to help generate life loss