All the posts about hiding objects in plain sight are nice and all, but if somebody ever becomes aware that 10M worth of valuables is in your abode, and you are not there, and there is no security in place, rest assured that stuff will be found and taken eventually.
Me personally, I would learn dark magic. It’s possible to hire a dark magician, but he could turn on you. So, then I will erect a massive tower, with only one entrance. This entrance will be sealed by a super powerful dark barrier, which can only be broken by gathering the eight artifacts of light.
These artifacts, which I would steal from the temple of light beforehand, are to be scattered around the world and hidden in eight different dungeons. Each item shall reside in the bottom of the dungeon, and will be guarded by a special “boss” monster. The boss monster shall be locked inside the artifact room with a special key. This special key can only be obtained by using a special item, which in turn can only be found in the temple by solving a series of puzzles and defeating various minions.
If any adventurer comes along and starts gathering artifacts, then I’ll use my magic to send him (or her), to the future or past, or cause massive shrinkage, or kidnap his or her SO, or partially destroy the world, or some combination of the above.
IF the adventurer succeeds after all this and manages to climb to the top of my dark tower where the valuables are being kept, then I’ll teleport the treasure to my actual secret hiding place and force the adventurer to fight a phantom version of myself.
Of course, there is one more safety step. If the adventurer then proceeds to defeat my phantom and discover my true hiding place, then I’d have no choice but to transform into my perfect form, thus ensuring GG NO RE. Game Over. The End.
So, whaddaya think?