Martrell's Floating Fortress

Whenever an artifact you control is put into your graveyard from the battlefield, put an armaments counter on Martrell's Floating Fortress.
As long as there are five or more armaments
counters on Martrell's Floating Fortress, it is
an artifact creature with base power and
toughness 5/5 with "{t}: Martrell's Floating
Fortress deals 4 damage to any target."