Similarly, a creature whose toughness is doubled gets +0/+X, where X is its toughness as the effect begins to apply
Its chosen at random, though, so that means you would have to sort through your entire deck, pick out all the basics, let your opponent see them, and figure out some way to select one randomly
In the case of Enduring Ideal, you're probably already running protective elements (Solitary Confinement, No Mercy, Sphere of Safety, etc.) to immediately tutor for, then once safe, you can begin grabbing more threatening enchantments
Finally, in the event you manage to roll a 20, you get to put a Creature card from any graveyard onto the battlefield under your control
Its combination of defensive utility and offensive potential has made it one of the standout cards in the Prismatic Evolutions set
The key is simple