The Dark Tower (3-6) - LEGO Harry Potter: Years 1-4
Shoot the green lamp. You need to shoot 5 of these to unlock the Blue Crest piece. Have your Patronum spell ready then continue to the right. Destroy the wraith along the way, then melt the ice covering the second lamp. Shoot the chest then use the hammer to destroy the rock covering the vines. Clear the vines then kill the wraith.
Next melt the ice covering the third lamp in the middle of the bridge. Head to the fountain and melt the ice. Shoot the fourth lamp afterward. Use WiLe to bring the water-filled bucket to the right side and water the seeds. Shoot the flowers and jump on them to reach the upper platform. Shoot the torch-holder to melt half the ice covering the door. Kill the wraith that will appear. You'll also find the fifth lamp here. Shoot the chest to the right then rebuild the second torch-holder. Shoot it so it melts the other half of the door. Enter the door when ready.
In this section, you'll need to split up. Use WiLe to place the first platform so your partner can proceed. Next, switch to your partner and use the torch to retract the vines and for the wooden palette to drop.
Switch to the character on the right side and continue forth. Place the platform again to the left, switch then use WiLe on the lego pieces to rebuild the path to the right. Switch then continue until you reach the door. Rebuild the path to the left using the debris blocking the door and regroup with your partner. Enter the next room to continue.
In the next area, use WiLe to bring the cauldron down. Use the WiLe again to the small barrel beside the tree. Use the axe to chop the branch where the flower piece is sitting on top off. Next, shoot the planter to the left then destroy the large snake that will appear. Grab the tooth piece. Next, jump/ climb down south and lift the purple gargoyle and place it above the window to smash it.
Take the Red Crest piece hiding to the right, then switch to Hermione and solve the puzzle cabinet. Grab the last piece and put it on the cauldron. Take note that two more wraiths will appear. Destroy them, use the strength potion then pull the chain to raise the bridge. Cross the bridge and go upstairs for a boss fight.
During this battle, you need to use multi-lock to destroy multiple wraiths faster. Harry's Patronum spell has a slight delay for every shot so using it normally by pressing B won't help that much. The pattern for this boss is simple. You need to use WiLe on the barrels until you find a plumber. Wait for it to absorb everything around it and the plumber will stuck on its face. This is the time its vulnerable so shoot it to deal damage. Repeat two more times to win the battle and complete the chapter.
Wraith boss battle
James Potter (Ghost) - After crossing the frozen bridge, turn left then blast the silver lock on the door.
After getting the character token above, blast the wraith to save the student in peril.
Lily Potter (Ghost) – After entering the building, unlock the chest right in front of you.
Green Crest piece - After getting across the ceiling, use Griphook to open the safe.
Sirius Black – In the third area, jump down south where the purple gargoyle is. Enter the room then destroy the dark cabinet to the left.
Yellow Crest piece - You need to shoot 6 silver gargoyles to get this piece. One is above the door where you came from, two are hanging to the south, there is one each in at the edge of the tree and statue (you'll get a better view of them while crossing the bridge), the last one is right before you go upstairs before crossing the bridge.