So first make sure you're at least level 7 (can be started at level 4) and that you have a good trained weapon and if possible, buy some cure light potions from the shop all west on the main street.
Starting from recall, go w, n, w, w, w, w, w, w, n, n, n, n, n, n, ne, n, n, n, n, e, e, e, n, n and kill one of the prospectors around there for a spade. Alternatively, there are are spades that repop in the graveyard area and near Master Irvin, or you can buy one from the General Store. Once you have the spade, head w, w, n, n, n, n, n, n, n, n, n, e, e, e, n, n, e, e, n, n, w, w, n, n, d, e, e, e, e, s, s, s, s, s, e, e, e, e, n, n, e, e, e, e, e, n, n, n and light your lantern. If you don't have a lantern because you've already used it up, you can buy torches from the shop south. Once you have a light, go d, s, s, w, w, s, s, s, s, e, e, n, e, e, n and kill the dryad. If the dryad is dead, wait for repop. You'll obtain a red leaf from her if you kill her. An alternative method has been added which you can see by LOOKing at the dryad - it involves giving her a water skin in exchange for the leaf.
Recall and wait to regenerate some stamina, then go w, n, w, w, w, w, w, w, n, n, w and dig. You should reveal a down, go down and kill the zombie who has already killed the dryad. If he's dead wait for repop and kill him. Once you have the second leaf, recall again.
N.b. for the next section, which involves getting the gold leaf from the room of the dragon, glowing footsteps have been added to Lasler which you can follow to get from the beginning of the forest to the dragon's cave.
Regen your stamina and go w, n, e, e, e, e, e, e, e, s, s, s, s, sw, se and wait for the dryad to open the tree then, s, w, se, s and again wait for the dryad to open the tree then e, s, w, w, n, n, w, sw, n, nw, e, ne, n, sw, w, n, w and this is where it gets tricky. To the west a dragon moves around, if the dragon attacks you it can kill you in one round and burn your equipment. So use look west to make sure the dragon isn't there, if he isn't go west but keep alert in case he walks in. West from this room is where the last leaf, which is gold, repops. It is dropped by the dragon, so you need to check every couple of minutes to see if it's in there. Dropping a torch or light on the ground is a good way to keep it lit up. Usually there's a fight for this leaf, so you'll need to be quick. Also remember, drop a lit torch in the room so you can look into the room to check when the dragon drops the leaf. The dragon must be in the room and awake for the leaf to be dropped, so if he sleeps wake him up. Once you have the leaf, go back out of the cave and recall, or go west and pull the parachute to be taken back near recall.
Regen your stamina and go w, n, e, e, e, e, e, e, e, s, s, s, s, sw, se and wait for the dryad to open the tree then, s, w, se, s and again wait for the dryad to open the tree then e, n, ne, and wait for the dryad to open the tree again, then ne, s, e. You need to dismount here, and the final dryad will ask you "What can you keep but give away?" There are three answers, either wisdom, knowledge, or word. Say one of them and a passage will open to the south, go through the passage and wear the gold leaf. Use it a couple of times until you're hasted, then follow the path until you're transferred into the trial.
Once you beat the mob, go north and get the Mark of Wisdom + manual for your trial, wear the manual and use it to raise whatever you get (is totally random). You will also receive a tome that gives experience points, which you can use immediately or save for when you require more experience per level (they need to be used before level 30 and have a timer on them). Recall and you are done and can move onto the Obelisk puzzle.