In most cases (see below), if you wait until the combat damage step or end of combat step, it will be after combat damage has been dealt, so the Ninja won't deal combat damage
In the event that you are pressed for life, even in a Commander game, Sylvan Library still lets you draw two cards and put two back, at the very least improving the quality of cards in your hand for a turn or two
You can also -2 him to make a 2/1 Ninka token for smashing and growing that loyalty or making unblockable
Common features a circle, with one edge around it and a dull, gray color
But times change, and now we have both smarter players and a little gem called Oracle
I have always thought Slivers were cool and interesting, and its been an idea of mine to build a Sliver deck for years