It is recommended to take three items so that you will not lose anything

Dragon Leather: Once you have successfully gathered a number of your chosen dragon hides, you will need to get them tanned (for 20 gp a time) before they are ready to be made into armour. However, with that done you can begin crafting cheap altis gates gold items as shown below:

It is the only altar in RuneScape, apart from the one you can use after completing Nature Spirit, in which praying at it will heal your Prayer Points and it'll add an extra two, but it doesn't raise your Prayer level, unfortunately.

For example, if somebody with 41 Prayer prays at the altar, they'll get 43/41 Prayer points. It doesn't mean that they can use the prayer, Protect from Melee, though.

The only disadvantage to this is the run to the bank. You are able to be attacked in this short run, but you most likely will make it safely to the bank. It is still recommended to only take three items so that you will not lose anything other than ores if you die from a PKer.

Inside the Guild: The guild does not have much in it. It has 37 rocks containing Coal and 5 rocks containing Mithril.