Wruihziakt has tamed the inner ghost inside of him, Wart. While Wart is inside of Zak, he can control his wild magic inside. Whereas if he is outside, Wart can manipulate wild magic at will and cause it to happen at a much faster pace. 

While Wart is inside Zak's body:

• After rolling for a Wild Magic Surge roll, you can choose to manipulate wild magic to be at a much higher frequency or not, causing the chances of it happening to increase. After rolling a d20 and get any number 5-2, you can choose to roll on the Wild Magic Surge table or not. If you get a 1, you cannot choose and always have to roll.

While Wart is outside Zak's body:

• It's an action to take Wart out of zak's body during a battle
• When Wart comes outside of Zak's body, it takes its hit points directly from Zak. It's hit points are equal to Zak's hit point maximum divided by two (rounded down). Zak loses this equal to his hit point maximum, meaning that his permanent hit points are drained.
• If Wart dies, he immediately goes back into Zak's body and is resurrected after a long rest. Zak cannot roll a Wild Magic Surge roll while Wart is dead
• Wart can enter back Zak's body even if he is outside. Zak regains his permanent hit point maximum, however, he can not restore any health Wart has left. 
• After Zak casts a spell he always rolls a Wild Magic Surge. Instead of rolling a d20 however, you roll a d2. If you roll a 1, roll on the Wild Magic Surge table
• After Wart takes damage, roll a d2. If you roll a 1, roll on the Wild Magic Surge table
• During Zak's turn, he can command Wart to always roll on the Wild Magic Surge table. This is considered a bonus action
• When you roll on the Wild Magic Surge table, all spells that are centered around yourself are centered directly around Zak. For example, if you roll a 20 and you cast Grease centered on yourself, Grease is centered directly on Zak