As you can see, your foe becomes a Monarch this turn when he ETBs, and you cannot swap over after your combat this turn
The original version of Dalakos was too complicated so they whittled him down into this form, which is

Advanced Search Sets Random Syntax Release date: 2012-07-05 Ajani, Caller of the Pride Ajani's Sunstriker Angel's Mercy Angelic Benediction Attended Knight Aven Squire Battleflight Eagle Captain of the Watch Captain's Call Crusader of Odric Divine Favor Divine Verdict Erase Faith's Reward Glorious Charge Griffin Protector Guardian Lions Guardians of Akrasa Healer of the Pride Intrepid Hero Knight of Glory Oblivion Ring Odric, Master Tactician Pacifism Pillarfield Ox Planar Cleansing Prized Elephant Rain of Blades Rhox Faithmender Safe Passage Serra Angel Serra Avatar Serra Avenger Show of Valor Silvercoat Lion Sublime Archangel Touch of the Eternal War Falcon War Priest of Thune Warclamp Mastiff Archaeomancer Arctic Aven Augur of Bolas Battle of Wits Clone Courtly Provocateur Divination Downpour Encrust Essence Scatter Faerie Invaders Fog Bank Harbor Serpent Hydrosurge Index Jace, Memory Adept Jace's Phantasm Kraken Hatchling Master of the Pearl Trident Merfolk of the Pearl Trident Mind Sculpt Negate Omniscience Redirect Rewind Scroll Thief Sleep Spelltwine Sphinx of Uthuun Stormtide Leviathan Switcheroo Talrand, Sky Summoner

This is probably the fourth version of this kind of card you want to play in Commander
Of those forms, our favourite pick for the Madam Mims best card in Rise of the Floodborn is Madam Mim, Fox
Most Tyranids have the new Ravenous mechanic, which draws a card for their controller if theyre cast for X=5 or more