Cheapest priced copy (Fallout): $0.49 at Card Kingdom, near mint, their price list as of .
Vault 87: Forced Evolution 
Enchantment — Saga · Rare · Fallout · #122
(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Gain control of target non-Mutant creature for as long as you control this Saga.
II — Put a +1/+1 counter on target creature you control. It becomes a Mutant in addition to its other types.
III — Draw cards equal to the greatest power among Mutants you control.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
2 printings · $0.49 to $3.49 at Card Kingdom
3 rulings from Wizards of the Coast
- 8 March 2024The target of Vault 87's first chapter ability only needs to be a non-Mutant when that ability is put onto the stack and when that ability resolves. The control effect won't end if it later becomes a Mutant (perhaps because of the effect of the second chapter ability).
- 8 March 2024If Vault 87 leaves the battlefield before its first chapter ability resolves, you won't gain control of the target creature at all.
- 8 March 2024Use the greatest power among Mutants you control as Vault 87's last ability resolves to determine how many cards to draw.