how do you use item codes in last legacy null space

[mariofan2014]

i tryed adding this but won,t go in, in any way. i,ma trying to add this llitem:{997}

[l.m]

I think you should remove the keys, so it stays like this:

llitem:997

[-BY]

As FrozenFire said. No braces are needed.
However keep in mind that you'll need another triggerbox activating the boss trigger via tagname, or else the enemy won't spawn in your level.