Wizards of the Coast senior narrative designer and TMNT narrative design lead Crystal Frasier began the preview explaining her role in designing this set, stating, "We're incredibly lucky with TMNT that a lot of our artists were already huge fans of the property, so a lot of them went above and beyond." As Magic: The Gathering fans already know, every card has just a hint of storytelling happening, even outside of the sometimes-included flavor text, and that hasn't changed with this set
This might seem like a low range but in practice Sunlance kills way more things
Not only is this an immensely powerful activated ability, but the fact that Ulamogs Dreadsire has vigilance means you can stay on the attack while also building up your board
The most likely reasons are if it's sacrificed, if it's legendary and another legendary permanent with the same name is controlled by the same player, if it's a planeswalker and another planeswalker with the same subtype is controlled by the same player, if it's a creature with toughness 0 or less, or if it's an Aura that's either unattached or attached to something illegal