Killa's Level Up Ability is best activated as soon as possible. However, a little planning ahead works well with Killa's Ability. However, nothing suggests that another room could not be built over top the last room in a player's dungeon and not get the +3 boost.
This card is very similar Scythe, however with a wound requirement.
There are 2 versions of this card. The GEN001 that was handed out during GenCon and the TNL004 meant for Boss Monster 2. The GEN001 version features a stony background, platforms, and a pile of bones next to Killa. In the TNL004 version, the background and platforms are changed, the pile of bones removed, and the title is changed slightly to feature "Ape" instead of "Gorilla". He also bares a resemblance to Donkey Kong.