What are all the ways to get them? what monsters drop them?
If it drops gems, it can drop a half.
You can also get them from caskets. The random event ones/fishing ones are the same. It’s a 1/128 chance each or 1/64 for any half.
is there a list of monsters that are on it? i know osrs has had monsters drop tables tweeked
If the monster has ~randomjewel it can drop halves.
I’ll just add that fire giants have a 1/12 to hit the table, moss 1/32 and reg giants have a 1/64. Most other mobs have 1/128 chances so the big guys are good to aim for. Shadow warriors after legends quest also have a really high rate, but pretty steep requirements for those.