Hollow Radiance
Hollow is great against Ornn, as it protects against his %HP magic damage brittle, but it also often allows you to perma-push into him.
Redemption
Redemption can be nice vs tanks, as it does 10% max HP true damage. You trade off being able to pop squishies (which TK loves) but it can be a nice consideration, as it's cheap and you can guarantee a hit with your ult.
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Weigh all your options. I think it's perfectly fine to just go Heartsteel if the rest of the map calls for it.