Kalamax, the Stormsire | Insidious Will

Cards

({2} magic symbol) ({U} magic symbol) ({U} magic symbol) plus the cost of the additional instant available.

Cast any instant by paying its mana cost.
Holding priority, cast
Insidious Will by paying its mana cost.
Kalamax's first and second abilities trigger.
Resolve the first ability, creating a copy of
Insidious Will and choosing to copy the original
Insidious Will.
Resolve the second ability, putting a +1/+1 counter on
Kalamax.
Resolve the
Insidious Will copy, creating a copy of
Insidious Will.
Kalamax's second ability triggers, putting a +1/+1 counter on itself.
Repeat from step 6 any number of times.

This combo has been estimated to be Oddball (Bracket 2-3+).