Post-damage-related: Sometimes it is important to wait until combat damage has resolved to use a combat-specific effect (like Heavy Ballista's)
Similarly, though, watch out for cards like Commanders Plate, which count Partners and Backgrounds when calculating a Commanders color identity which means Karlach will always be more than just red if you pick a different colored Background
Three cost mana-generating artifacts have to be really interesting these days to get a look-in from players
Tinybones Joins Up Tinybones Joins Up makes opponents discard the moment it lands, and then adds extra pain whenever your legendaries enter
There is no traveling, no scheduling conflicts, and relatively minimal costs
Obviously, this doesnt quite get there, but it seems fine This looks pretty good