I have just completed 15 multi-battles at level 13 of Ice Golums Peak trying to get 5 5* or higher artefacts all I got was two tankards and a load of extra money. I ran the level in the normal way and got an artefact. 

NB The team I used none of them died, the team consists of Duchess Lilitu, Trunda Giltmallett, Jizoh, Athel and Shirimani. All are 6* and fully ascended except the Duchess who has  one of her 6* not ascened.