Do you like running them in your decks
For Silverquil small creatures become casualties on the way to free copies of spells, and Witherbloom turns each of your creatures into a cost reducer
It's fairly typical of Black creatures, like Vampire, to be able to sacrifice another creature to gain a boost either temporary, like Bloodthrone Vampire , or permanent, like Bloodflow Connoisseur
The downside is that the creature is exiled at the end of the turn, meaning youll need to consistently put creatures into your graveyard through self-mill, sacrifice, or discard
At first glance that sounds like, "Why would you want to have less health?" But it allows you to use Level Ball (AOR 76/98), which searches your deck for 90 HP or less, so you can search out the Combee and you can search out Vespiquen
Higher populations may moderate PSA 10 premiums for common GX cards