Astute Knight Castellan

If you have 5 or more Maintenance counters, you
may pay {u}{u} instead of its normal mana cost.
hexproof
When Astute Knight Castellan attacks, the
defending players' creatures get -3/-0 until end
turn. Whenever Astute Knight Castellan deals
combat damage to a player, draw three cards.
Become your Knight, as it becomes you, and through symbiosis ascend. So shall you become. So shall you protect your people and slaughter your foes.