While they can mostly only be used while on the battlefield, you should read the ability and look for clues as to when its supposed to be used
Instead of reducing their opponents health to zero, in Disney Lorcana both players are racing to be the first to reach 20 lore, acquired by questing with cards and using certain abilities
Its effect to pay the top card of your library is easy to accomplish and can be done at instant speed, so even if you have removal for Urza, the effect can be used multiple times before it ever resolves
Whenever you proliferate during your turn, draft a card from Contagion Dispensers spellbook
Is this number more inflated for red and white decks, and combat decks, than for other archetypes and colors
A second commander that wasnt as juiced would still let players put all their favorite Vampires together without worry over becoming that player