The reason you can’t find any Biblical basis for those claims is because THERE ARE NONE! The words cardinal and butterfly are not mentioned once in the Bible so that is enough to refute such claims. So, it is NOT BIBLICAL. Is it demonic? Surely the devil, who is the “father of lies” (see John 8:44), would love people to believe such nonsense. If you read the account of angelic visitors, you will see that they either appeared in the form of a man (see Genesis 18:1-2 with 19:1-3; Daniel 9:20-21; Mark 16:5-6 and Acts 1:9-11)) or in their true, spiritual form (see Genesis 32:1-2; Matthew 2:13; Luke 2:8-15a). Regarding a “loved one” who has died appearing on earth, the Bible clearly teaches that their departed spirits (see James 2:26) are either with Lord (Acts 7:59-60; 2nd Corinthians 5:6-8) or in a place of torment awaiting the final judgment (Luke 16:19-23). There is not one verse in Scripture which would teach (directly or indirectly) that their spirits can return to earth at will in another form in order to visit loved ones.

There has always been a fascination in people’s minds regarding angels. I had a question posted recently about people claiming to see angels on video cameras and those who have posted such pictures are doing so to draw attention to themselves. Some “pastors” are even gathering large crowds to their “churches” and taking in a lot of money as well from these curious souls who have come to be blessed by “visiting angels.” As we saw in my answer, angels would never appear to draw attention to themselves OR to the “church leaders” who are supposedly posting pictures of them. In many cases it is a scheme to acquire money and in other cases it boils down to “the worshipping of angels.” The apostle Paul warned against this very thing in Colossians 2:18, “Let no one cheat you of your reward, taking delight in false humility and WORSHIP OF ANGELS, INTRUDING INTO THOSE THINGS WHICH HE HAS NOT SEEN, vainly puffed up by his fleshly mind.” In Revelation chapter 22 we see that John himself fell into this snare: “Now I, John, saw and heard these things. And when I heard and saw, I FELL DOWN TO WORSHIP BEFORE THE FEET OF THE ANGEL WHO SHOWED ME THESE THINGS” (verse 8). How did the angel react? Ah, he quickly said, “See that you do not do that. For I am your fellow servant, and of your brethren the prophets, and of those who keep the words of this book” (verse 9). Angels are “ministering spirits sent forth to minister for those who will inherit salvation.” They are glad to serve the Lord in this way and their desire to bring glory to Him alone, and never to themselves.

I conclude that all reports of angels or loved ones appearing to people on earth in the form of a cardinal or butterfly is pure nonsense. This idea comes from the “father of lies” who loves to appeal to our EMOTIONS to give us “false comfort” and to distract us from the One we should be occupied with, the Lord Jesus Christ. There is only one time that I can think of where God allowed two men to come back to earth in a human form and we learn in that account that Jesus, who was also there, was the One to be worshipped. Here is the passage: “Now after six days Jesus took Peter, James, and John, and led them up on a high mountain apart by themselves; and He was transfigured before them. His clothes became shining, exceedingly white, like snow, such as no launderer on earth can whiten. And ELIJAH APPEARED TO THEM WITH MOSES, and they were talking with Jesus. Then Peter answered and said to Jesus, ‘Rabbi, it is good for us to be here; and let us make three tabernacles: one for You, one for Moses, and one for Elijah’—because he did not what to say, for they were greatly afraid. And a cloud came and overshadowed them; and a voice came out of the cloud, saying, ‘This is My beloved Son. Hear Him!’ Suddenly, when they had looked around, THEY SAW NO ONE ANYMORE, BUT ONLY JESUS with themselves” (Mark 9:2:8).  (483.5)  (DO)