If the tentacle summoned by Ozumat’s Hero Power gets turned into its golden variant in combat by Yu’lon, the stats get reset into it’s default stats of 6/6.
Easiest way to reproduce is to have max 6 minions going into combat so the Hero Power summons the tentacle before Yu’lon’s effect activates. The tentacle is a tier 1 minion so it’s the most likely target too.