The size of the second spell you cast determines how big of a spell you can steal, so you should look to cast spells that are free or reduce their mana cost, like Force of Will and Dig Through Time
This thing beats the hell out of you if you fail to hinder it in some way
If you want, you can turn it into Isilu, Carrier of Twilight, which gives your creatures persist
TLDR: The stated goal of the Mythic rarity at its conception was four-fold
Peace Offering wants you to give your opponents a card draw while drawing cards yourself as you spread counters on creatures to buff them up for attacks
This useful card will give two lore when questing, and every time she quests, two damage counters from one character can be moved to an opposing character instead, therefore giving the player lore, healing, and damaging the opponent in one move