By forcing them to stay exerted, you also keep them vulnerable to additional challenges, making it far more risky for your rivals to use their characters with this card in your deck
A number of dedicated buy, sell, and trade groups for MTG have cropped up in recent years, and while I primarily use them for buying individual cards, Ill occasionally pick up some sealed products like booster boxes here as well
If it's an artifact or creature card, you may reveal it and put it into your hand
Characters like Gramma Tala and Mickey Mouse, Detective will help boost a players Inkwell, while Aurora, Dreaming Guardian potentially Wards an entire party early in the game
You don't need to wait for a five-cost Dragon Fire - anything from a two ink card like Freeze to ostensibly helpful actions like Healing Glow will do the trick
Damaging yourself is debatably a downside, but you are rewarded by a massive 4/4 Lifelinker once you drop under half life with this effect