Gripping the rim and base of the urn, you heave it up and over the lip of the tomb. As you jump away, you realise that perhaps there was something slightly unusual about those silver coins. What spills out of the pot into the tomb more resembles molten lava than currency. Some kind of liquid fire joins the black mass in the tomb.
The effects are immediate. The host of tentacles writhes and snaps about, before whipping back towards the tomb and being sucked into the same pores they emerged from. The skin of the black thing is beginning to bubble and crack in the heat, and in a much shorter time than would be expected reduces itself to an unsightly goo.
The whole mess, organic and molten, rapidly cools, and before long a hard sludge has come to rest in the bottom of the sarcophagus. You cautiously approach, and there is no sign of activity. It is apparently dead - if it were even alive to begin with.