If you’re gearing up for a brutal black dragon slayer grind, I get the excitement — these things actually feel worthwhile to kill. In my runs I always see the typical dragon-stuffs first: dragon bones and black dragonhide are the consistent staples, so they’re the bread-and-butter profit. Beyond that you’ll commonly pick up coins, a steady trickle of runes (think common combat runes like nature/chaos/death depending on your method), seeds and herbs (grimy herbs drop regularly), and the odd uncut gem or two. Those little resource drops add up over long tasks and keep you selling stuff to the bank between respawns.
On the rarer side there’s a miscellaneous table that can hand you higher-value items — occasional rune equipment, some mid-tier rares, and the kinds of drops that make you stop and check your inventory properly. Loot is pretty similar to other high-level dragons but skewed toward better herbs/runes and more consistent bones/hide. If you want exact probabilities, the OSRS Wiki lists the full drop table and rates; for casual planning though, expect steady dragon bones + hides, decent rune/coin skims, and an occasional gem or rare piece that spices up your bank balance. I always leave a slayer task with a smile when the hide and bones stack up, so it’s a reliable way to grind and unwind.