Most board buff creatures like this dont affect themselves, so this is a nice bit of upside
The actual way that the card will typically function is that each player will choose a number (and write it down to prevent them from changing it later and to prove they were thinking of that number), and each player will lose life equal to that number with the player who wrote the smallest number losing half of their life
If Frodo, Adventurous Hobbit and Sam, Loyal Attendant are your commanders, your deck may contain cards with white, black, and/or green in their color identity, but not blue or red
Then if youre the monarch, double the number of +1/+1 counters on each creature you control
Zodiark, Umbral God Embrace the blackness and get Zodiark who is an undeniably indestructible, mass murdering threat to the game
Equilibrium (Tempest/Stronghold/Exodus) You'll hear me use the word "tempo" a lot when describing limited cards