Halloween is a day of celebrating Evil Spirits and the dead. From skeletons, zombies, and monsters that have supposedly come to life on this evening, to little devils roaming the streets playing evil pranks, this day of “Halloween” is thoroughly devoted to one power, and one alone- Satan, and his realm of evil, sin, and death.
God is very clear in HIS witness to us that one “CAN NOT” expect to be considered Christian (a follower of Jesus Christ) by Him, IF they choose to practice such a ritual as “Halloween”:
1 Cor. 10:20-22 (KJV)
But I say, that the things which the Gentiles sacrifice, they sacrifice to devils, and not to God: and I would not that ye should have fellowship with devils.
 YE CANNOT drink the cup of the Lord, AND the cup of devils: YE CANNOT be partakers of the Lord’s table, AND of the table of devils.
 Do we provoke the Lord to jealousy? are we stronger than he?
2 Cor. 6:14-7:1 (NASB)
DO NOT be bound together with unbelievers;
for WHAT PARTNERSHIP HAVE RIGHTEOUSNESS AND LAWLESSNESS,
or WHAT FELLOWSHIP HAS LIGHT WITH DARKNESS?
 Or WHAT HARMONY HAS CHRIST WITH BELIAL,
or what has a believer in common with an unbeliever?
 Or what agreement has the temple of God with idols?
For we are the temple of the living God; just as God said,
“I will DWELL IN THEM AND WALK AMONG THEM;
And I will be their God, and they shall be My people.
 “Therefore, come out from their midst and be separate,” says the Lord.
“AND DO NOT touch WHAT IS UNCLEAN;
AND I WILL WELCOME YOU.
 “And I will be a father to you,
And you shall be sons and daughters to Me,”
Says the Lord Almighty.
[7:1] THEREFORE, having these promises, beloved, LET US CLEANSE OURSELVES FROM ALL DEFILEMENT OF FLESH AND SPIRIT, perfecting holiness in the fear of God.
Deut. 32:16-20 (KJV)
They provoked him to jealousy with strange gods, with abominations provoked they him to anger.
 They sacrificed unto devils, not to God; to gods whom they knew not, to new gods that came newly up, whom your fathers feared not.  Of the Rock that begat thee thou art unmindful, and hast forgotten God that formed thee.
 And when The LORD saw it, He abhorred them, because of the provoking of His sons, and of His daughters.  And HE SAID, I WILL HIDE MY FACE FROM THEM, I will see what their end shall be: for they are a very froward generation, children in whom is no faith.
Psalm 106:35-37 (KJV)
…were mingled among the heathen, and learned their works.  And they served their idols: which were a snare unto them.  Yea, they sacrificed their sons and their daughters unto devils…
God also clearly WARNS anyone who would choose to practice these rituals that are contrary and stand in defiance to the things that He delights in:
Isaiah 65:12-15 (KJV)
…Therefore will I number you to the sword, and ye shall all bow down to the slaughter: BECAUSE when I called, ye did not answer; WHEN I SPAKE, YE DID NOT HEAR; BUT DID EVIL BEFORE MINE EYES, AND DID CHOOSE THAT WHEREIN I DELIGHTED NOT.
 Therefore thus saith the Lord God, Behold, my servants shall eat, but ye shall be hungry: behold, my servants shall drink, but ye shall be thirsty: behold, my servants shall rejoice, but ye shall be ashamed:  Behold, my servants shall sing for joy of heart, but ye shall cry for sorrow of heart, AND shall howl for vexation of spirit.  AND ye shall leave your name for a curse unto my chosen: FOR THE LORD GOD SHALL SLAY THEE, and call his servants by another name:
God delights in all righteous and loving behavior- which is anything that is a part of a lifestyle of LAWFUL behavior:
Ezekiel 18:4-9 (KJV)
Behold, ALL SOULS are mine; as the soul of the father, so also the soul of the son is mine: THE SOUL THAT SINNETH, IT SHALL DIE.
 BUT if a man be just, AND DO THAT WHICH IS LAWFUL AND RIGHT,  And hath not eaten upon the mountains, neither hath lifted up his eyes to the idols of the house of Israel, neither hath defiled his neighbour’s wife, neither hath come near to a menstruous woman,  And hath not oppressed any, but hath restored to the debtor his pledge, hath spoiled none by violence, hath given his bread to the hungry, and hath covered the naked with a garment;  He that hath not given forth upon usury, neither hath taken any increase, that hath WITHDRAWN his hand from INIQUITY………
Ezekiel 18:30 (KJV)
Therefore I will judge you, O house of Israel, every one according to his ways, saith The Lord GOD. REPENT, and TURN YOURSELVES FROM ALL YOUR TRANSGRESSIONS; so INIQUITY shall not be your ruin.
Acts 2:38 (KJV)
Then Peter said unto them, REPENT, and be baptized every one of you in the name of Jesus Christ FOR THE REMISSION OF SINS, and ye shall receive the gift of the Holy Ghost.
1 John 3:4 (NASB)
EVERYONE WHO PRACTICES SIN also PRACTICES LAWLESSNESS; and SIN IS LAWLESSNESS.
Rev. 2:5 (NASB)
‘REMEMBER therefore from where you have fallen, AND REPENT and do the deeds you did at first; OR ELSE I am coming to you, and will remove your lampstand out of its place– UNLESS YOU REPENT.
………that hath WITHDRAWN his hand FROM INIQUITY, hath executed true judgment between man and man,  Hath WALKED IN MY STATUTES, and HATH KEPT MY JUDGMENTS, TO DEAL TRULY; HE IS JUST, HE SHALL SURELY LIVE, saith the Lord God.
Romans 13:8-14 (KJV)
Owe no man any thing, but to LOVE ONE ANOTHER: for he that loveth another hath fulfilled the law.  For THIS, Thou shalt not commit adultery, Thou shalt not kill, Thou shalt not steal, Thou shalt not bear false witness, Thou shalt not covet; AND IF THERE BE ANY OTHER COMMANDMENT, it is briefly comprehended in this saying, namely, Thou shalt love thy neighbour as thyself.
 LOVE WORKETH NO ILL TO his neighbour: THEREFORE LOVE IS THE FULFILLING OF THE LAW.
1 John 5:3 (KJV)
For THIS is the love of God, THAT WE KEEP HIS COMMANDMENTS: and his commandments are not grievous.
 And that, knowing the time, that now it is high time to awake out of sleep: for now is our salvation nearer than when we believed.  The night is far spent, the day is at hand: let us therefore cast off the works of darkness, and let us put on the armour of light.  Let us walk honestly, as in the day; NOT IN rioting and drunkenness, not in chambering and wantonness, not in strife and envying.
 BUT PUT YE ON THE LORD JESUS Christ, and MAKE NOT PROVISION FOR THE FLESH, TO FULFIL THE LUSTS thereof.
The Truth (God’s Word) stands as a witness against us, telling us that we WILL NOT ENTER The Kingdom of God IF WE CHOOSE to practice evil, sin, UN-righteous behavior in our life:
Galatians 5:19-21 (KJV)
Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness,  Idolatry, WITCHCRAFT, hatred, variance, emulations, wrath, strife, seditions, heresies,  Envyings, murders, drunkenness, REVELLINGS, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God.
Rev. 22:15 (NASB)
OUTSIDE ARE the dogs and the sorcerers and the immoral persons and the murderers and the idolaters, and EVERYONE WHO LOVES AND PRACTICES LYING.
1 Cor. 6:9-11 (KJV)
Know ye not that THE UNRIGHTEOUS SHALL NOT INHERIT THE KINGDOM OF GOD?
Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind,  Nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners, shall inherit the kingdom of God.  And such WERE some of you: but ye are washed, BUT YE ARE sanctified, but YE ARE justified in the name of the Lord Jesus, and by the Spirit of our God.
For further study on exactly how The Truth (The Word of God) condemns the celebrating of mankind’s traditional “holidays” (whether it be the worship of devils, or the departure of “all hallows”) RATHER THAN following The Way of faith that PRACTICES OBEDIENCE TO THE COMMANDMENTS OF GOD (Father of Jesus Christ), you may refer to the following list of relevant studies: