Eternal Oath is the merging of the bands Mindrot and Aphrodisiac featuring the combined line-up of Ted Jonsson (drums), Joni Maensivu (vocals), Petri Tarvainen (guitar) and Ted Lundstrom (bass), with Daniel Dziuba joining on as second guitarist shortly later to become a part of the Melodic Death Metal movement of the 1990s. In December of 1992 they recorded a 3-song demo titled simply Demo to see what they could accomplish and they were pleased with the results. Ted, however, would leave the band shortly after to join Amon Amarth with Martin Wiklandertaking his place. Due to this change, however, the demo was never released. A year later, they would try their hands at recording again and a 5-song demo was the result. Art Of Darkness showed the band wandering off the Death Metal path and onto a more melodic leaning. Daniel Dziuba, however, would not follow the path any further and was replaced by Peter Nagy (from Hypocrite and Mork Gryning).
In February 1994 they recorded another 3 song demo titled simply Promo and got a response from 'Rat Pack Records', who subsequently released it as a mini-CD. By 1995 'Rat Pack' still hadn't released their latest demo so the band broke the contract to release So Silent on their own. Martin Wicklander would be the next victim of changes; he would leave and be replaced by Peter Wendin who had been playing as a session drummer with them in the mean time. Another temporary member would be Pär Almqvist (keyboard) for live shows in 1996.
Their first full-length album, published by 'Pulverized', Through The Eyes Of Hatred would be released in 2000.
Their new album, Righteous, would arrive in 2002 on VME' and was re-released in 2004 on Black Lodge Records', due to Pulverized going bankrupt, before heading on another tour. Through their short history they have played with bands such as At The Gates, Unanimated, Necrophobic, Acanorous Quintet, Dissection, Impious and Ablaze My Sorrow to name a few.
After over 15 years of activity, the band suddenly dissolved in early 2007, with some previous members going on to form Faceshift.
In 2011, the band announced a reformation, in-line with the act's 20th anniversary. The new line-up consists of 4 of the founding members, with Peter Nagy-Eklof and Petri Tarvainen on guitar, Ted Jonsson on drums and Joni Mäensivu on vocals. Two new members, Mika Kajanen on bass and Johan Adler on keyboards are also featured to release Ghostlands in 2013.