Moritte of the Frost by paying ({2} magic symbol) ({G} magic symbol) ({U} magic symbol) ({U} magic symbol) , choosing to have it enter the battlefield as a copy of
Havi.
Put
Moritte of the Frost into your graveyard due to the legend rule.
When
Moritte of the Frost dies, it and
Havi trigger.
Resolve the
Havi trigger, returning
Moritte of the Frost from your graveyard to the battlefield as a copy of
Havi.
Repeat from step 2.
Resolve all
Moritte of the Frost triggers from step 3, returning all legendary creature card(s) with mana value 5 or less from your graveyard to the battlefield.
Results
Infinite LTB.
Infinite ETB.
Infinite death triggers.
Put all legendary creature cards with mana value 5 or less from your graveyard onto the battlefield.