Havan

According to Gurmukh Sense Havan can be explained as the Burning of Panj Vikars in Agg/Fire of Naam. Havan as a Ritual is not a Part of Sikhism it was introduced by Sikhs of Nirmala Sect who Infiltrated into the Khalsa Panth(Main Stream Sikhs). Also the pangti quoted in my understanding is the sewa lakh paat done in nimrata state will guarantee victory

At the end of Brahm Kavach, the last line of Dohra which goes "Paatth sava laakh havan kar jeet jung tab hog". Which basically means "When you do 1,25,000 Paatths of Brahm Kavach along with the Havan, you shall be victorious in the battlefield". Here we Should note that Guru Sahib is not telling us to do the Ritualistic Havan but to Burn Our 5 Vikars which are kaam (lust), krodh (wrath), lobh (greed), moh (attachment) and ahankar (ego or excessive pride).

Some Nihangs perform Havan as a Ritual which is Wrong according to Gurmat. Evidence claims that in old times Nihang Singhs used to Do Gurbani Santhiya, Read Sakhiyaan, and Sing Kirtan near the Fire because It used to be the Only Light Source Big Enough to Light thier Make Shift Camp's. But it later became a Ritual much like the Hindu Havan after Khalsa Panth was Infiltrated.