This ability makes it so if a character under your control is challenged, so long as Tiana is exerted, your opponents character gets -3 strength unless its owner pays three ink
Because of this, the useful guideline for playing any kind of lifegain card is that it has to be substantially overpowered relative to damage-dealing cards to be playable, at all
There are a couple though
One of the times it isnt good is in decks that have a lot of colored pips, and for those occasions, Sceptre of Eternal Glory is here to offer you a deal: if you can get three lands with the same name into play, you can have three colored mana instead of three colorless
One leading contender was a landfall theme to play up the battle for Gaia and its Lifestream, but that ended up feeling too ambiguous
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