
Ultimecia, Time Sorceress | Legendary Creature | Human Warlock | Whenever Ultimecia enters or attacks, surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)
At the beginning of your end step, you may pay {4}{U}{U}{B}{B} and exile eight cards from your graveyard. If you do, transform Ultimecia. | Mikio Masuda

Cloud of Darkness | Legendary Creature | Avatar | Flying
Particle Beam — When Cloud of Darkness enters, target creature an opponent controls gets -X/-X until end of turn, where X is the number of permanent cards in your graveyard. | Fariba Khamseh

Kefka, Court Mage | Legendary Creature | Human Wizard | Whenever Kefka enters or attacks, each player discards a card. Then you draw a card for each card type among cards discarded this way.
{8}: Each opponent sacrifices a permanent of their choice. Transform Kefka. Activate only as a sorcery. | Xui Ton