When Skemfar Shadowsage enters, choose one —
• Each opponent loses X life, where X is the greatest number of creatures you control that have a creature type in common.
• You gain X life, where X is the greatest number of creatures you control that have a creature type in common.
You choose which mode the triggered ability has as you put that ability on the stack. You can't change modes later.
05-02-2021
wotc
The amount of life lost or gained is calculated as the triggered ability resolves based on the creatures you control at that time, including Skemfar Shadowsage itself if it's still under your control. You'll always use the greatest number possible. You don't need to choose any creature types. For example, if you control a Giant Wizard, a Giant Warrior, an Elf Warrior, and a Kor Warrior at that time, each opponent will lose 3 life or you'll gain 3 life.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.