THIS IS fine, I'd say especially for more useful items, there is a limit to the fusion before they split apart again and there should b e so many times he can do it in a day (so if it he finds a garbage can, he can't make 100 hammers).
DICEROLL WOULD BE FUNNY, if he tries to merge them and it ends up being like a slapchop or something instead of a hammer.
ACCEPTED + ADDENDUM, MERGE LAYERS is the first thing I thought of
DICEROLL WOULD BE FUNNY, if he tries to merge them and it ends up being like a slapchop or something instead of a hammer.