Activate Lavaclaw Reaches's ability so that it becomes a creature.
Activate it to give it +0/+0 until end of turn infinite times to get infinite Construct triggers.
Repeat.

Infinitely large Crackdown Construct until end of turn

Crackdown Construct

Lavaclaw Reaches

Activate Lavaclaw Reaches's last ability by paying {1}{B}{R}, causing it to become a 2/2 Elemental creature with a new ability until end of turn.
Activate that new ability by paying {0}.
Ceaseless Searblades triggers, getting +1/+0 until end of turn.
Resolve Lavaclaw Reaches's ability, having no effect.
Repeat from step 2.

Combos with "Lavaclaw Reaches"