Update 19.5 Scythe, Pole-arm and Staff Weapons ListScythe
• Ether Reaper
• Reaper PrimePole-arm
• Orthos Prime
• Sydon Vaykor
• Bo Mk1
• Bo Prime
• Broken Scepter (Reward for completing The War Within)
Mk.1 Weapons you can buy for Credits from the Marketplace and provide quick replacements.
There are quite a few of these weapons as Blueprints on the marketplace, like Orthos, Bo and Anku.
Lot's of weapons require a Mastery Rank, but by leveling weapons you increase your Rank so this shouldn't be a problem, just make sure to Rank up regularly.Check here for required Mastery Ranks
or the Marketplace.
Prime Weapons require Void completion, often high level Survival/Defense 'Rotation C' drops. These are endgame. I use Primarch Prime Part Guide
The Scythe Hate is acquired from defeating the Stalker.
.Leveling weapons to Rank 30
The best way to level weapons is to play Survival or Defense missions and kill lots of enemies, then extract for the bonus exp, you'll get lots of weapon mastery whilst unlocking all worlds, doing alerts, unlocking other achievements and just playing the game. Remember to always swap for you next weapon and have one ready to swap.
Lots of Dark Sectors have Affinity bonus (+Shotgun), use a Warframe that supports you but doesn't really kill enemies so you rely on your weapons, being in a group spawns more enemies for more exp.
Elara on Jupiter is a great mission for Affinity, as the anti-moas spawn early and often, and they give a fair amount of affinity around 7-9x the exp of grunts.