From the RuneScape Wiki, the wiki for all things RuneScape

Wizard Cromperty

Release date	Unknown edit
Race	Human
Members NPC?	Yes
Quest NPC?	Yes- Tribal Totem, One Small Favour, King's Ransom, Back to my Roots
Location	East Ardougne
Sells items?	No
Skill requirement?	No
Quest requirement?	No
Gender	Male
Examine	The hat is a dead give away.
Notable features	Wizard and inventor.

Wizard Cromperty is in this building in north-east Ardougne

Wizard Cromperty is a wizard-inventor living in the North East corner of East Ardougne near the mining patch. While having two jobs, he creates magic inventions. His best invention to date is his patented pending teleport block, a pair of blocks teleporting the user from one block to another. Hoping to demonstrate it to the staff at the Wizard Tower, he sent the package to the RPDT Postal Service to deliver it. The package is never delivered and the player can interchange the Address label of the crate in the RPDT depot with one of Lord Hazelmort's packages during the Tribal Totem quest.

Wizard Cromperty can teleport players to Rune essence and talk about his invention, bragging a little on the matter. He is involved in the Tribal Totem quest as indicated above. He also plays a role in the One Small Favour quest to create an Animate rock scroll to rescue Petra, trapped in a rock wall in the Goblin Cave near the Fishing Guild. He is also present in the King's Ransom quest to release King Arthur from imprisonment in a rock statue in the basement of the Black Knights' Fortress. Finally, he is in the Back to my Roots quest, asking the player to check his parcel at the RPDT depot. Unintentionally, Cromperty starts the Returning Clarence miniquest by finding his severed hand in the parcel.

Once a player gets the Ardougne cloak 2, he/she can see Wizard Cromperty each day (resetting at midnight GMT [Players logged in before midnight GMT will have to log out for him to have reset]) to get 100 free Pure Essence. Furthermore, when the Hard tasks of the Ardougne Achievement Diary are achieved, thus, when a player obtains the Ardougne cloak 3, Wizard Cromperty gives 150 free Pure Essence instead of 100.

Trivia

• Wizard Cromperty wears a Cape of legends, so it is possible he is a member of the Legends' Guild.
• He is apparently a good friend of Sedridor as he says so each time a player talks to him; Merlin also mentions him as a friend and possesses knowledge of his teleporting people into stone, suggesting you seek his aid in freeing King Arthur from Morgan's spell.
• Wizard Cromperty has a lot of references to The Wonderful Wizard of Oz in the Back to my Roots quest.
• There is a hammer and a chisel spawn in his house.
• The RuneScape Manual is misleading as it states "In addition to the easy and medium tasks' reward, when worn:" implying Wizard Cromperty should provide the 150 rewarded from task 3 on top of the 100 rewarded by task 2 (250 in total).